Categories of Network:

Network can be divided in to two main categories:

• Peer-to-peer.
• Server – based.

In peer-to-peer networking there are no dedicated servers or hierarchy among the computers. All of the computers are equal and therefore known as peers. Normally each computer serves as Client/Server and there is no one assigned to be an administrator responsible for the entire network.

Peer-to-peer networks are good choices for needs of small organizations where the users are allocated in the same general area, security is not an issue and the organization and the network will have limited growth within the foreseeable future.

The term Client/server refers to the concept of sharing the work involved in processing data between the client computer and the most powerful server computer.

The client/server network is the most efficient way to provide:

• Databases and management of applications such as Spreadsheets, Accounting, Communications and Document management.
• Network management.
• Centralized file storage.

The client/server model is basically an implementation of distributed or cooperative processing. At the heart of the model is the concept of splitting application functions between a client and a server processor. The division of labor between the different processors enables the application designer to place an application function on the processor that is most appropriate for that function. This lets the software designer optimize the use of processors--providing the greatest possible return on investment for the hardware.

Client/server application design also lets the application provider mask the actual location of application function. The user often does not know where a specific operation is executing. The entire function may execute in either the PC or server, or the function may be split between them. This masking of application function locations enables system implementers to upgrade portions of a system over time with a minimum disruption of application operations, while protecting the investment in existing hardware and software.

The OSI Model:

Open System Interconnection (OSI) reference model has become an International standard and serves as a guide for networking. This model is the best known and most widely used guide to describe networking environments. Vendors design network products based on the specifications of the OSI model. It provides a description of how network hardware and software work together in a layered fashion to make communications possible. It also helps with trouble shooting by providing a frame of reference that describes how components are supposed to function.

There are seven to get familiar with and these are the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and the application layer.

• Physical Layer, is just that the physical parts of the network such as wires, cables, and there media along with the length. Also this layer takes note of the electrical signals that transmit data throughout system.
• Data Link Layer, this layer is where we actually assign meaning to the electrical signals in the network. The layer also determines the size and format of data sent to printers, and other devices. Also I don't want to forget that these are also called nodes in the network. Another thing to consider in this layer is will also allow and define the error detection and correction schemes that insure data was sent and received.
• Network Layer, this layer provides the definition for the connection of two dissimilar networks.
• Transport Layer, this layer allows data to be broken into smaller packages for data to be distributed and addressed to other nodes (workstations).
• Session Layer, this layer helps out with the task to carry information from one node (workstation) to another node (workstation). A session has to be made before we can transport information to another computer.
• Presentation Layer, this layer is responsible to code and decode data sent to the node.
• Application Layer, this layer allows you to use an application that will communicate with say the operation system of a server. A good example would be using your web browser to interact with the operating system on a server such as Windows NT, which in turn gets the data you requested.

Types of Networks:

LANs (Local Area Networks)

A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people. The development of standard networking protocols and media has resulted in worldwide proliferation of LANs throughout business and educational organizations.

WANs (Wide Area Networks)

Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines (both synchronous and asynchronous), satellite links, and data packet carrier services. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols and filters to minimize the expense of sending data sent over vast distances.

Internet

The Internet is a system of linked networks that are worldwide in scope and facilitate data communication services such as remote login, file transfer, electronic mail, the World Wide Web and newsgroups.

With the meteoric rise in demand for connectivity, the Internet has become a communications highway for millions of users. The Internet was initially restricted to military and academic institutions, but now it is a full-fledged conduit for any and all forms of information and commerce. Internet websites now provide personal, educational, political and economic resources to every corner of the planet.

Intranet

With the advancements made in browser-based software for the Internet, many private organizations are implementing intranets. An intranet is a private network utilizing Internet-type tools, but available only within that organization. For large organizations, an intranet provides an easy access mode to corporate information for employees.

MANs (Metropolitan area Networks)

The refers to a network of computers with in a City.

VPN (Virtual Private Network)

VPN uses a technique known as tunneling to transfer data securely on the Internet to a remote access server on your workplace network. Using a VPN helps you save money by using the public Internet instead of making long–distance phone calls to connect securely with your private network. There are two ways to create a VPN connection, by dialing an Internet service provider (ISP), or connecting directly to Internet.

What is a computer Network?

A network is any collection of independent computers that communicate with one another over a shared network medium.A computer network is a collection of two or more connected computers. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives. When networks at multiple locations are connected using services available from phone companies, people can send e-mail, share links to the global Internet, or conduct video conferences in real time with other remote users. As companies rely on applications like electronic mail and database management for core business operations, computer networking becomes increasingly more important.

Every network includes:

• At least two computers Server or Client workstation.
• Networking Interface Card's (NIC)
• A connection medium, usually a wire or cable, although wireless communication between networked computers and peripherals is also possible.
• Network Operating system software, such as Microsoft Windows NT or 2000, Novell NetWare, Unix and Linux.

HOW TO HACK FACEBOOK WITH THE HELP OF KEYLOGGER

Hack Facebook password is using Keyloggers.

Today i will explain you how to hack Facebook password using keylogger.

how to create your Facebook hacker keylogger, its a 100% Fully undetectable keylogger you can check this file using Virus total. Its a 100% FUD remote keylogger with several advanced features.
its so easy that anyone can do it. On my website you will never get any infected tool. If you have any doubt or feel something suspicious always test the link or file with virus total website before downloading. Never believe any website including mine also, always scan download links with virus total website or any such website before downloading it. Download it only when it does not have any virus.


Hack Facebook password using Keylogger Involves following steps:
1. Create your Server that will hack passwords.
2. Extract the Icons from any software
3. Bind the Keylogger to make it Hidden
4. Spread your keylogger to victims

Note: This tutorial is for Educational Purposes only. I and Isoftdl is not responsible for any misuse of knowledge.

Let's start Facebook hacking tutorial in detail :


STEP1 : Create Server for Hacking Passwords
First of all for hacking any facebook account password, we have to create our keylogger server that will run on victims machine or PC and capture his keystrokes and mail us on the email account that we will use to build the keylogger. The keylogger server building process consists of several steps.
The steps involved are mentioned below in detail:
1. First of all download the Keylogger.
http://www.mediafire.com/?t5z9wneqs426q9d

DOWNLOAD BINDER HERE: http://www.mediafire.com/?1udgufwivk0vdmg

2. Extract the RAR file. Now you will get one Folder and three files

3. Now open the Keylogger file. Here you will need gmail ID and password. For safer use create a fake Gmail account

Facebook Hacker Initial Step

4. Now Click on server settings as shown. Here enter the time after which you want to receive reports, its always preferable to use 20 min timer for receiving files. And Click on Output box to choose location of file and give it any name. Its always recommended to use system process name to make it undetectable like svchost or check any process name from your task manager and name it. Other fields are optional. The complete snapshot is shown below:

Second step to choose time interval and name of output file
5. Now Click on Log and Result Setting. In Log EMail Title enter the subject of email like My keylogger report or simply my report or something else that you like. Also Click the last two options that i.e add Computer name and add victim name.

6. Now Click on Other Options. In this section you just have to do one thing. Most hackers prefer warning message POP up but I love keylogger using any message. So unclick message button. Because when you bind it with any other software then it should not any warning messages otherwise it will be detectable.

7. Now at last click on Build Keylogger. Now after you click on it you will see your keylogger file at location that you have chosen in 4th step. Now this keylogger server file will be used to bind with any other software in Binding Step.

8. Now you keylogger server is ready that you will use to hack Facebook accounts. That's all for the server creation step now move to second main step.



Step 2.: Extracting the Icon file from any installer(resource hacker)
1. Open the Resource hacker folder and open the reshacker file.
2. Now go to its menu and open any setup file. Suppose we want to attach our keylogger to Ccleaner setup file. So open the Ccleaner setup with resource hacker.
3. Now in menu there is one action button click on it and then click save all resources.
4. Now save all the resources to desktop or any other location of your choice.
5. It consists of two files one is icon file and other is res file . We only need icon file, so you can delete the other file i.e res file.
6. Now we have Icon of installer file(as discussed above Ccleaner setup Icon).

<span>Step 3: Bind the Keylogger server with any software</span>
1. Now Go to keylogger folder and open the Binder.
2. Now Click on + button given below to add files.
3. Now add the keylogger server and the set up of software (i.e. in our case it's Ccleaner setup).
4. Now in menu of Binder, Go to Settings. There select the icon that we have generated in the previous step and set the location of output file as shown in figure.
5. Now again go to File's menu in Binder and click on Bind files.
6. Now your Binded keylogger is ready. Now you have to spread it or send it to the victim that is your friend.

<span>Step4 : How to Spread Keylogger or send it to victim or friend</span>
1. Now you have one Software setup file with keylogger attached with it.(In our case we have Ccleaner setup with keylogger attached with it.
2. Now Spread your keylogger through forums. You might be a member of various forums use them to spread your keylogger in form of software posts. You can use various software's to spread them that users frequently download.
3. Spread it through pendrives or USB hard drives. Suppose a friend asked you for a software give it the software that has keylogger attached with it.
Note: you can also attach keylogger with images also. But that can be detectable by antivirus. So avoid such type of hacking.
So isn't that so easy to hack anyone's Facebook account in just few minutes.

How to protect yourself from these hacks?
Prevention is always better than cure so always follow these steps:
1. Don't use cracked softwares and don't download them from unauthorized websites.
2. Always keep your antivirus and anti-spyware up to date.
3. Always scan the files before transferring them to your USB.
4. Do not allow other users to use your PC i.e password protect it.

Thanks Shrinath Dagabaj

About CVE Identifiers

CVE Identifiers (also called "CVE names," "CVE numbers," "CVE-IDs," and "CVEs") are unique, common identifiers for publicly known information security vulnerabilities. CVE identifiers have "entry" or "candidate" status. Entry status indicates that the CVE Identifier has been accepted to the CVE List while candidate status (also called "candidates," "candidate numbers," or "CANs") indicates that the identifier is under review for inclusion in the list.

	Each CVE Identifier includes the following: CVE Identifier number (i.e., "CVE-1999-0067"). Indication of "entry" or "candidate" status. Brief description of the security vulnerability or exposure. Any pertinent references (i.e., vulnerability reports and advisories or OVAL-ID).

Understanding Your Computer: Operating Systems

The operating system is the most fundamental program that runs on your computer. It serves as the basis for how everything else works. 

  What is an operating system?

An operating system (OS) is the main program on a computer. It performs a variety of functions, including

• determining what types of software you can install
• coordinating the applications running on the computer at any given time
• making sure that individual pieces of hardware, such as printers, keyboards, and disk drives, all communicate properly
• allowing applications such as word processors, email clients, and web browsers to perform tasks on the system (e.g., drawing windows on the screen, opening files, communicating on a network) and use other system resources (e.g., printers, disk drives)
• reporting error messages

The OS also determines how you see information and perform tasks. Most operating systems use a graphical user interface (GUI), which presents information through pictures (icons, buttons, dialog boxes, etc.) as well as words. Some operating systems can rely more heavily on textual interfaces than others.

How do you choose an operating system?

In very simplistic terms, when you choose to buy a computer, you are usually also choosing an operating system. Although you may change it, vendors typically ship computers with a particular operating system. There are multiple operating systems, each with different features and benefits, but the following three are the most common:

• Windows - Windows, with versions including Windows XP, Windows Vista, and Windows 7, is the most common operating system for home users. It is produced by Microsoft and is typically included on machines purchased in electronics stores or from vendors such as Dell or Gateway. The Windows OS uses a GUI, which many users find more appealing and easier to use than text-based interfaces.
• Mac OS X - Produced by Apple, Mac OS X is the operating system used on Macintosh computers. Although it uses a different GUI, it is conceptually similar to the Windows interface in the way it operates.
• Linux and other UNIX-derived operating systems - Linux and other systems derived from the UNIX operating system are frequently used for specialized workstations and servers, such as web and email servers. Because they are often more difficult for general users or require specialized knowledge and skills to operate, they are less popular with home users than the other options. However, as they continue to develop and become easier to use, they may become more popular on typical home user systems.

Benefits of BCC

Although in many situations it may be appropriate to list email recipients in the To: or CC: fields, sometimes using the BCC: field may be the most desirable option. 

 What is BCC?

BCC, which stands for blind carbon copy, allows you to hide recipients in email messages. Addresses in the To: field and the CC: (carbon copy) field appear in messages, but users cannot see addresses of anyone you included in the BCC: field.

Why would you want to use BCC?

There are a few main reasons for using BCC:

• Privacy - Sometimes it's beneficial, even necessary, for you to let recipients know who else is receiving your email message. However, there may be instances when you want to send the same message to multiple recipients without letting them know who else is receiving the message. If you are sending email on behalf of a business or organization, it may be especially important to keep lists of clients, members, or associates confidential. You may also want to avoid listing an internal email address on a message being sent to external recipients. 
•  Another point to remember is that if any of the recipients use the "reply to all" feature to reply to your messages, all of the recipients listed in the To: and CC: fields will receive the reply. If there is potential for a response that is not appropriate for all recipients, consider using BCC.
  
• Tracking - Maybe you want to access or archive the email message you are sending at another email account. Or maybe you want to make someone, such as a supervisor or team member, aware of the email without actually involving them in the exchange. BCC allows you to accomplish these goals without advertising that you are doing it.
• Respect for your recipients - People often forward email messages without removing the addresses of previous recipients. As a result, messages that are repeatedly sent to many recipients may contain long lists of email addresses. Spammers and email-borne viruses may collect and target those addresses. To reduce the risk, encourage people who forward messages to you to use BCC so that your email address is less likely to appear in other people's inboxes and be susceptible to being harvested. To avoid becoming part of the problem, in addition to using BCC if you forward messages, take time to remove all existing email addresses within the message. The additional benefit is that the people you're sending the message to will appreciate not having to scroll through large sections of irrelevant information to get to the actual message.
  

How do you BCC an email message?

Most email clients have the option to BCC listed a few lines below the To: field. However, sometimes it is a separate option that is not listed by default. If you cannot locate it, check the help menu or the software's documentation.
If you want to BCC all recipients and your email client will not send a message without something in the To: field, consider using your own email address in that field. In addition to hiding the identity of other recipients, this option will enable you to confirm that the message was sent successfully.

Benefits and Risks of Free Email Services

Although free email services are convenient for sending personal correspondence, you should not use them to send messages containing sensitive information. 

 What is the appeal of free email services?

Many service providers offer free email accounts (e.g., Yahoo!, Hotmail, Gmail). These email services typically provide you with a browser interface to access your mail. In addition to the monetary savings, these services often offer other benefits:

• accessibility - Because you can access your account(s) from any computer, these services are useful if you cannot be near your computer or are in the process of relocating and do not have an ISP. Even if you are able to access your ISP-based email account remotely, being able to rely on a free email account is ideal if you are using a public computer or a shared wireless hot spot and are concerned about exposing the details of your primary account.
• competitive features - With so many of these service providers competing for users, they now offer additional features such as large amounts of storage, spam filtering, virus protection, and enhanced fonts and graphics.
• additional capabilities - It is becoming more common for service providers to package additional software or services (e.g., instant messaging) with their free email accounts to attract customers.

Free email accounts are also effective tools for reducing the amount of spam you receive at your primary email address. Instead of submitting your primary address when shopping online, requesting services, or participating in online forums, you can set up a free secondary address to use.

What risks are associated with free email services?

Although free email services have many benefits, you should not use them to send sensitive information. Because you are not paying for the account, the organization may not have a strong commitment to protecting you from various threats or to offering you the best service. Some of the elements you risk are

• security - If your login, password, or messages are sent in plain text, they may easily be intercepted. If a service provider offers SSL encryption, you should use it. You can find out whether this is available by looking for a "secure mode" or by replacing the "http:" in the URL with "https:".
• privacy - You aren't paying for your email account, but the service provider has to find some way to recover the costs of providing the service. One way of generating revenue is to sell advertising space, but another is to sell or trade information. Make sure to read the service provider's privacy policy or terms of use to see if your name, your email address, the email addresses in your address book, or any of the information in your profile has the potential of being given to other organizations. If you are considering forwarding your work email to a free email account, check with your employer first. You do not want to violate any established security policies.
• reliability - Although you may be able to access your account from any computer, you need to make sure that the account is going to be available when you want to access it. Familiarize yourself with the service provider's terms of service so that you know exactly what they have committed to providing you. For example, if the service ends or your account disappears, can you retrieve your messages? Does the service provider give you the ability to download messages that you want to archive onto your machine? Also, if you happen to be in a different time zone than the provider, you may find that their server maintenance interferes with your normal email routine.

Understanding Encryption

Encrypting data is a good way to protect sensitive information. It ensures that the data can only be read by the person who is authorized to have access to it. 

What is encryption?

In very basic terms, encryption is a way to send a message in code. The only person who can decode the message is the person with the correct key; to anyone else, the message looks like a random series of letters, numbers, and characters. Encryption is especially important if you are trying to send sensitive information that other people should not be able to access. Because email messages are sent over the internet and might be intercepted by an attacker, it is important to add an additional layer of security to sensitive information.

How is it different from digital signatures?

Like digital signatures, public-key encryption utilizes software such as PGP, converts information with mathematical algorithms, and relies on public and private keys, but there are differences:

• The purpose of encryption is confidentiality—concealing the content of the message by translating it into a code. The purpose of digital signatures is integrity and authenticity—verifying the sender of a message and indicating that the content has not been changed. Although encryption and digital signatures can be used independently, you can also sign an encrypted message.
• When you sign a message, you use your private key, and anybody who has your public key can verify that the signature is valid. When you encrypt a message, you use the public key for the person you're sending it to, and his or her private key is used to decrypt the message. Because people should keep their private keys confidential and should protect them with passwords, the intended recipient should be the only one who is able to view the information.

How does encryption work?

1. Obtain the public key for the person you want to be able to read the information. If you get the key from a public key ring, contact the person directly to confirm that the series of letters and numbers associated with the key is the correct fingerprint.
2. Encrypt the email message using their public key. Most email clients have a feature to easily perform this task.
3. When the person receives the message, he or she will be able to decrypt it.

Understanding Digital Signatures

Digital signatures are a way to verify that an email message is really from the person who supposedly sent it and that it hasn't been changed. 

What is a digital signature?

There are different types of digital signatures; this tip focuses on digital signatures for email messages. You may have received emails that have a block of letters and numbers at the bottom of the message. Although it may look like useless text or some kind of error, this information is actually a digital signature. To generate a signature, a mathematical algorithm is used to combine the information in a key with the information in the message. The result is a random-looking string of letters and numbers.

Why would you use one?

Because it is so easy for attackers and viruses to "spoof" email addresses, it is sometimes difficult to identify legitimate messages. Authenticity may be especially important for business correspondence—if you are relying on someone to provide or verify information, you want to be sure that the information is coming from the correct source. A signed message also indicates that changes have not been made to the content since it was sent; any changes would cause the signature to break.

How does it work?

Before you can understand how a digital signature works, there are some terms you should know:

• Keys - Keys are used to create digital signatures. For every signature, there is a public key and a private key.
  • Private key - The private key is the portion of the key you use to actually sign an email message. The private key is protected by a password, and you should never give your private key to anyone.
  • Public key - The public key is the portion of the key that is available to other people. Whether you upload it to a public key ring or send it to someone, this is the key other people can use to check your signature. A list of other people who have signed your key is also included with your public key. You will only be able to see their identities if you already have their public keys on your key ring.
• Key ring - A key ring contains public keys. You have a key ring that contains the keys of people who have sent you their keys or whose keys you have gotten from a public key server. A public key server contains keys of people who have chosen to upload their keys.
• Fingerprint - When confirming a key, you will actually be confirming the unique series of letters and numbers that comprise the fingerprint of the key. The fingerprint is a different series of letters and numbers than the chunk of information that appears at the bottom of a signed email message.
• Key certificates - When you select a key on a key ring, you will usually see the key certificate, which contains information about the key, such as the key owner, the date the key was created, and the date the key will expire.
• "Web of trust" - When someone signs your key, they are confirming that the key actually belongs to you. The more signatures you collect, the stronger your key becomes. If someone sees that your key has been signed by other people that he or she trusts, he or she is more inclined to trust your key. Note: Just because someone else has trusted a key or you find it on a public key ring does not mean you should automatically trust it. You should always verify the fingerprint yourself.

The process for creating, obtaining, and using keys is fairly straightforward:

1. Generate a key using software such as PGP, which stands for Pretty Good Privacy, or GnuPG, which stands for GNU Privacy Guard.
2. Increase the authenticity of your key by having your key signed by co-workers or other associates who also have keys. In the process of signing your key, they will confirm that the fingerprint on the key you sent them belongs to you. By doing this, they verify your identity and indicate trust in your key.
3. Upload your signed key to a public key ring so that if someone gets a message with your signature, they can verify the digital signature.
4. Digitally sign your outgoing email messages. Most email clients have a feature to easily add your digital signature to your message.

There are a variety of mechanisms for creating digital signatures, and these mechanisms may operate differently. For example, S/MIME does not add a visible block of letters and numbers within the message, and its digital signatures are verified indirectly using a certificate authority instead of directly with other users in a web of trust. You may just see an icon or note on the message that the signature has been verified. If you get an error about a digital signature, try to contact the sender through a phone call or a separate email address that you know is valid to verify the authenticity of the message.

Coordinating Virus and Spyware Defense

Using anti-virus and anti-spyware software is an important part of cyber security. But in an attempt to protect yourself, you may unintentionally cause problems. 

Isn't it better to have more protection?

Spyware and viruses can interfere with your computer's ability to process information or can modify or destroy data. You may feel that the more anti-virus and anti-spyware programs you install on your computer, the safer you will be. It is true that not all programs are equally effective, and they will not all detect the same malicious code. However, by installing multiple programs in an attempt to catch everything, you may introduce problems.

How can anti-virus or anti-spyware software cause problems?

It is important to use anti-virus and anti-spyware software. But too much or the wrong kind can affect the performance of your computer and the effectiveness of the software itself.
Scanning your computer for viruses and spyware uses some of the available memory on your computer. If you have multiple programs trying to scan at the same time, you may limit the amount of resources left to perform your tasks. Essentially, you have created a denial of service against yourself. It is also possible that in the process of scanning for viruses and spyware, anti-virus or anti-spyware software may misinterpret the virus definitions of other programs. Instead of recognizing them as definitions, the software may interpret the definitions as actual malicious code. Not only could this result in false positives for the presence of viruses or spyware, but the anti-virus or anti-spyware software may actually quarantine or delete the other software.

How can you avoid these problems?

• Investigate your options in advance - Research available anti-virus and anti-spyware software to determine the best choice for you. Consider the amount of malicious code the software recognizes, and try to find out how frequently the virus definitions are updated. Also check for known compatibility issues with other software you may be running on your computer.
• Limit the number of programs you install - Many vendors are now releasing packages that incorporate both anti-virus and anti-spyware capabilities together. However, if you decide to choose separate programs, you really only need one anti-virus program and one anti-spyware program. If you install more, you increase your risk for problems.
• Install the software in phases - Install the anti-virus software first and test it for a few days before installing anti-spyware software. If problems develop, you have a better chance at isolating the source and then determining if it is an issue with the software itself or with compatibility.
• Watch for problems - If your computer starts processing requests more slowly, you are seeing error messages when updating your virus definitions, your software does not seem to be recognizing malicious code, or other issues develop that cannot be easily explained, check your anti-virus and anti-spyware software.

Browsing Safely: Understanding Active Content and Cookies

Many people browse the Internet without much thought to what is happening behind the scenes. Active content and cookies are common elements that may pose hidden risks when viewed in a browser or email client. 

What is active content?

To increase functionality or add design embellishments, web sites often rely on scripts that execute programs within the web browser. This active content can be used to create "splash pages" or options like drop-down menus. Unfortunately, these scripts are often a way for attackers to download or execute malicious code on a user's computer.

• JavaScript - JavaScript is just one of many web scripts (other examples are VBScript, ECMAScript, and JScript) and is probably the most recognized. Used on almost every web site now, JavaScript and other scripts are popular because users expect the functionality and "look" that it provides, and it's easy to incorporate (many common software programs for building web sites have the capability to add JavaScript features with little effort or knowledge required of the user). However, because of these reasons, attackers can manipulate it to their own purposes. A popular type of attack that relies on JavaScript involves redirecting users from a legitimate web site to a malicious one that may download viruses or collect personal information.
• Java and ActiveX controls - Different from JavaScript, Java and ActiveX controls are actual programs that reside on your computer or can be downloaded over the network into your browser. If executed by attackers, untrustworthy ActiveX controls may be able to do anything on your computer that you can do (such as running spyware and collecting personal information, connecting to other computers, and potentially doing other damage). Java applets usually run in a more restricted environment, but if that environment isn't secure, then malicious Java applets may create opportunities for attack as well.

JavaScript and other forms of active content are not always dangerous, but they are common tools for attackers. You can prevent active content from running in most browsers, but realize that the added security may limit functionality and break features of some sites you visit. Before clicking on a link to a web site that you are not familiar with or do not trust, take the precaution of disabling active content. These same risks may also apply to the email program you use. Many email clients use the same programs as web browsers to display HTML, so vulnerabilities that affect active content like JavaScript and ActiveX often apply to email. Viewing messages as plain text may resolve this problem.

What are cookies?

When you browse the Internet, information about your computer may be collected and stored. This information might be general information about your computer (such as IP address, the domain you used to connect (e.g., .edu, .com, .net), and the type of browser you used). It might also be more specific information about your browsing habits (such as the last time you visited a particular web site or your personal preferences for viewing that site). Cookies can be saved for varying lengths of time:

• Session cookies - Session cookies store information only as long as you're using the browser; once you close the browser, the information is erased. The primary purpose of session cookies is to help with navigation, such as by indicating whether or not you've already visited a particular page and retaining information about your preferences once you've visited a page.
• Persistent cookies - Persistent cookies are stored on your computer so that your personal preferences can be retained. In most browsers, you can adjust the length of time that persistent cookies are stored. It is because of these cookies that your email address appears by default when you open your Yahoo! or Hotmail email account, or your personalized home page appears when you visit your favorite online merchant. If an attacker gains access to your computer, he or she may be able to gather personal information about you through these files.

To increase your level of security, consider adjusting your privacy and security settings to block or limit cookies in your web browser. To make sure that other sites are not collecting personal information about you without your knowledge, choose to only allow cookies for the web site you are visiting; block or limit cookies from a third-party. If you are using a public computer, you should make sure that cookies are disabled to prevent other people from accessing or using your personal information.

Recognizing and Avoiding Spyware

Because of its popularity, the internet has become an ideal target for advertising. As a result, spyware, or adware, has become increasingly prevalent. When troubleshooting problems with your computer, you may discover that the source of the problem is spyware software that has been installed on your machine without your knowledge. 

 What is spyware?

Despite its name, the term "spyware" doesn't refer to something used by undercover operatives, but rather by the advertising industry. In fact, spyware is also known as "adware." It refers to a category of software that, when installed on your computer, may send you pop-up ads, redirect your browser to certain web sites, or monitor the web sites that you visit. Some extreme, invasive versions of spyware may track exactly what keys you type. Attackers may also use spyware for malicious purposes. Because of the extra processing, spyware may cause your computer to become slow or sluggish. There are also privacy implications:

• What information is being gathered?
• Who is receiving it?
• How is it being used?

How do you know if there is spyware on your computer?

The following symptoms may indicate that spyware is installed on your computer:

• you are subjected to endless pop-up windows
• you are redirected to web sites other than the one you typed into your browser
• new, unexpected toolbars appear in your web browser
• new, unexpected icons appear in the task tray at the bottom of your screen
• your browser's home page suddenly changed
• the search engine your browser opens when you click "search" has been changed
• certain keys fail to work in your browser (e.g., the tab key doesn't work when you are moving to the next field within a form)
• random Windows error messages begin to appear
• your computer suddenly seems very slow when opening programs or processing tasks (saving files, etc.)

How can you prevent spyware from installing on your computer?

To avoid unintentionally installing it yourself, follow these good security practices:

• Don't click on links within pop-up windows - Because pop-up windows are often a product of spyware, clicking on the window may install spyware software on your computer. To close the pop-up window, click on the "X" icon in the titlebar instead of a "close" link within the window.
• Choose "no" when asked unexpected questions - Be wary of unexpected dialog boxes asking whether you want to run a particular program or perform another type of task. Always select "no" or "cancel," or close the dialog box by clicking the "X" icon in the titlebar.
• Be wary of free downloadable software - There are many sites that offer customized toolbars or other features that appeal to users. Don't download programs from sites you don't trust, and realize that you may be exposing your computer to spyware by downloading some of these programs.
• Don't follow email links claiming to offer anti-spyware software - Like email viruses, the links may serve the opposite purpose and actually install the spyware it claims to be eliminating.

As an additional good security practice, especially if you are concerned that you might have spyware on your machine and want to minimize the impact, consider taking the following action:

• Adjust your browser preferences to limit pop-up windows and cookies - Pop-up windows are often generated by some kind of scripting or active content. Adjusting the settings within your browser to reduce or prevent scripting or active content may reduce the number of pop-up windows that appear. Some browsers offer a specific option to block or limit pop-up windows. Certain types of cookies are sometimes considered spyware because they reveal what web pages you have visited. You can adjust your privacy settings to only allow cookies for the web site you are visiting.

How do you remove spyware?

• Run a full scan on your computer with your anti-virus software - Some anti-virus software will find and remove spyware, but it may not find the spyware when it is monitoring your computer in real time. Set your anti-virus software to prompt you to run a full scan periodically.
• Run a legitimate product specifically designed to remove spyware - Many vendors offer products that will scan your computer for spyware and remove any spyware software. Popular products include Lavasoft's Ad-Aware, Microsoft's Window Defender, Webroot's SpySweeper, and Spybot Search and Destroy.
• Make sure that your anti-virus and anti-spyware software are compatible - Take a phased approach to installing the software to ensure that you don't unintentionally introduce problems.

Recovering from Viruses, Worms, and Trojan Horses

Unfortunately, many users are victims of viruses, worms, or Trojan horses. If your computer gets infected with malicious code, there are steps you can take to recover. 

How do you know your computer is infected?

Unfortunately, there is no particular way to identify that your computer has been infected with malicious code. Some infections may completely destroy files and shut down your computer, while others may only subtly affect your computer's normal operations. Be aware of any unusual or unexpected behaviors. If you are running anti-virus software, it may alert you that it has found malicious code on your computer. The anti-virus software may be able to clean the malicious code automatically, but if it can't, you will need to take additional steps.

What can you do if you are infected?

1. Minimize the damage - If you are at work and have access to an IT department, contact them immediately. The sooner they can investigate and clean your computer, the less damage to your computer and other computers on the network. If you are on your home computer or a laptop, disconnect your computer from the internet. By removing the internet connection, you prevent an attacker or virus from being able to access your computer and perform tasks such as locating personal data, manipulating or deleting files, or using your computer to attack other computers.
2. Remove the malicious code - If you have anti-virus software installed on your computer, update the virus definitions (if possible), and perform a manual scan of your entire system. If you do not have anti-virus software, you can purchase it at a local computer store. If the software can't locate and remove the infection, you may need to reinstall your operating system, usually with a system restore disk that is often supplied with a new computer. Note that reinstalling or restoring the operating system typically erases all of your files and any additional software that you have installed on your computer. After reinstalling the operating system and any other software, install all of the appropriate patches to fix known vulnerabilities.

How can you reduce the risk of another infection?

Dealing with the presence of malicious code on your computer can be a frustrating experience that can cost you time, money, and data. The following recommendations will build your defense against future infections:

• use and maintain anti-virus software - Anti-virus software recognizes and protects your computer against most known viruses. However, attackers are continually writing new viruses, so it is important to keep your anti-virus software current.
• change your passwords - Your original passwords may have been compromised during the infection, so you should change them. This includes passwords for web sites that may have been cached in your browser. Make the passwords difficult for attackers to guess.
• keep software up to date - Install software patches so that attackers can't take advantage of known problems or vulnerabilities. Many operating systems offer automatic updates. If this option is available, you should enable it.
• install or enable a firewall - Firewalls may be able to prevent some types of infection by blocking malicious traffic before it can enter your computer. Some operating systems actually include a firewall, but you need to make sure it is enabled.
• use anti-spyware tools - Spyware is a common source of viruses, but you can minimize the number of infections by using a legitimate program that identifies and removes spyware.
• follow good security practices - Take appropriate precautions when using email and web browsers so that you reduce the risk that your actions will trigger an infection.

As a precaution, maintain backups of your files on CDs or DVDs so that you have saved copies if you do get infected again.

Understanding Hidden Threats: Corrupted Software Files

Malicious code is not always hidden in web page scripts or unusual file formats. Attackers may corrupt types of files that you would recognize and typically consider safe, so you should take precautions when opening files from other people. 

What types of files can attackers corrupt?

An attacker may be able to insert malicious code into any file, including common file types that you would normally consider safe. These files may include documents created with word processing software, spreadsheets, or image files. After corrupting the file, an attacker may distribute it through email or post it to a web site. Depending on the type of malicious code, you may infect your computer by just opening the file.

When corrupting files, attackers often take advantage of vulnerabilities that they discover in the software that is used to create or open the file. These vulnerabilities may allow attackers to insert and execute malicious scripts or code, and they are not always detected. Sometimes the vulnerability involves a combination of certain files (such as a particular piece of software running on a particular operating system) or only affects certain versions of a software program.

What problems can malicious files cause?

There are various types of malicious code, including viruses, worms, and Trojan horses. However, the range of consequences varies even within these categories. The malicious code may be designed to perform one or more functions, including

• interfering with your computer's ability to process information by consuming memory or bandwidth (causing your computer to become significantly slower or even "freeze")
• installing, altering, or deleting files on your computer
• giving the attacker access to your computer
• using your computer to attack other computers.

How can you protect yourself?

Use and maintain anti-virus software - Anti-virus software recognizes and protects your computer against most known viruses, so you may be able to detect and remove the virus before it can do any damage. Because attackers are continually writing new viruses, it is important to keep your definitions up to date.

Use caution with email attachments - Do not open email attachments that you were not expecting, especially if they are from people you do not know. If you decide to open an email attachment, scan it for viruses first. Not only is it possible for attackers to "spoof" the source of an email message, but your legitimate contacts may unknowingly send you an infected file.

Be wary of downloadable files on web sites - Avoid downloading files from sites that you do not trust. If you are getting the files from a supposedly secure site, look for a web site certificate. If you do download a file from a web site, consider saving it to your computer and manually scanning it for viruses before opening it.

Keep software up to date - Install software patches so that attackers cannot take advantage of known problems or vulnerabilities. Many operating systems offer automatic updates. If this option is available, you should enable it.

Take advantage of security settings - Check the security settings of your email client and your web browser. Apply the highest level of security available that still gives you the functionality you need