What is a computer virus?

What is a computer virus?

A computer virus is a small software program that spreads from one computer to another computer and that interferes with computer operation. A computer virus may corrupt or delete data on a computer, use an e-mail program to spread the virus to other computers, or even delete everything on the hard disk.

Computer viruses are most easily spread by attachments in e-mail messages or by instant messaging messages. Therefore, you must never open an e-mail attachment unless you know who sent the message or unless you are expecting the e-mail attachment. Computer viruses can be disguised as attachments of funny images, greeting cards, or audio and video files. Computer viruses also spread by using downloads on the Internet. Computer viruses can be hidden in pirated software or in other files or programs that you may download.

Symptoms that may be the result of ordinary Windows functions

A computer virus infection may cause the following problems:
Note: These problems may also occur because of ordinary Windows functions or problems in Windows that are not caused by a computer virus.

• Windows does not start even though you have not made any system changes or even though you have not installed or removed any programs.
• Windows does not start because certain important system files are missing. Additionally, you receive an error message that lists the missing files.
• The computer sometimes starts as expected. However, at other times, the computer stops responding before the desktop icons and the taskbar appear.
• The computer runs very slowly. Additionally, the computer takes longer than expected to start.
• You receive out-of-memory error messages even though the computer has sufficient RAM.
• New programs are installed incorrectly.
• Windows spontaneously restarts unexpectedly.
• Programs that used to run stop responding frequently. Even if you remove and reinstall the programs, the issue continues to occur.
• A disk utility such as Scandisk reports multiple serious disk errors.
• A partition disappears.
• The computer always stops responding when you try to use Microsoft Office products.
• You cannot start Windows Task Manager.
• Antivirus software indicates that a computer virus is present.

Symptoms of a computer virus

If you suspect or confirm that your computer is infected with a computer virus, obtain the current antivirus software. The following are some primary indicators that a computer may be infected:

• The computer runs slower than usual.
• The computer stops responding, or it locks up frequently.
• The computer crashes, and then it restarts every few minutes.
• The computer restarts on its own. Additionally, the computer does not run as usual.
• Applications on the computer do not work correctly.
• Disks or disk drives are inaccessible.
• You cannot print items correctly.
• You see unusual error messages.
• You see distorted menus and dialog boxes.
• There is a double extension on an attachment that you recently opened, such as a .jpg, .vbs, .gif, or .exe. extension.
• An antivirus program is disabled for no reason. Additionally, the antivirus program cannot be restarted.
• An antivirus program cannot be installed on the computer, or the antivirus program will not run.
• New icons appear on the desktop that you did not put there, or the icons are not associated with any recently installed programs.
• Strange sounds or music plays from the speakers unexpectedly.
• A program disappears from the computer even though you did not intentionally remove the program.

Note These are common signs of infection. However, these signs may also be caused by hardware or software problems that have nothing to do with a computer virus. Unless you run the Microsoft Malicious Software Removal Tool, and then you install industry-standard, up-to-date antivirus software on your computer, you cannot be certain whether a computer is infected with a computer virus or not.

Symptoms of worms and trojan horse viruses in e-mail messages

When a computer virus infects e-mail messages or infects other files on a computer, you may notice the following symptoms:

• The infected file may make copies of itself. This behavior may use up all the free space on the hard disk.
• A copy of the infected file may be sent to all the addresses in an e-mail address list.
• The computer virus may reformat the hard disk. This behavior will delete files and programs.
• The computer virus may install hidden programs, such as pirated software. This pirated software may then be distributed and sold from the computer.
• The computer virus may reduce security. This could enable intruders to remotely access the computer or the network.
• You receive an e-mail message that has a strange attachment. When you open the attachment, dialog boxes appear, or a sudden degradation in system performance occurs.
• Someone tells you that they have recently received e-mail messages from you that contained attached files that you did not send. The files that are attached to the e-mail messages have extensions such as .exe, .bat, .scr, and .vbs extensions.

What is Spyware?

Spyware can install on your computer without your knowledge. These programs can change your computer’s configuration or collect advertising data and personal information. Spyware can track internet searching habits and possibly redirect web site activity.

Symptoms of Spyware

When a computer becomes affected by Spyware, the following may result:

• Slow internet connection.
• Changing your web browser’s home page.
• Loss of internet connectivity.
• Failure to open some programs, including security software.
• Unable to visit specific websites, which may include redirecting you to another one.

How to remove a computer virus and spyware.

Even for an expert, removing a computer virus or spyware can be a difficult task without the help of computer malicious software removal tools. Some computer viruses and other unwanted softwarereinstall themselves after the viruses and spyware have been detected and removed. Fortunately, by updating the computer and by using malicious software removal tools, you can help permanently remove unwanted software.

To remove a computer virus and other malicious software, follow these steps:

Install the latest updates from Microsoft Update:

1. For Windows Vista and Windows 7:
   1. Click the Pearl (Start) button, then type Windows Update in the search box.
   2. In the results area, click Windows Update.
   3. Click Check for Updates.
   4. Follow the instructions to download and install the latest Windows Updates.
2. For Windows XP:
   1. Click Start, then click Run.
   2. Type sysdm.cpl and press the Enter key.
   3. Click the Automatic Updates tab and choose the Automatic (recommended) option.
   4. Click OK.

Use the Microsoft Safety Scanner

Microsoft offers a free online tool that will scan and remove potential threats from your computer. To perform the scan, visit: http://www.microsoft.com/security/scanner/

Install and run Microsoft Security Essentials

Microsoft offers a free malicious removal program; Microsoft Security Essentials that will also help protect your computer from being infected. To install Microsoft Security Essentials, follow the steps below:

1. Go to the Microsoft Security Essentials
2. Click Download Now.
3. If your browser prompts you to save or run the file, click Run.
4. Follow the steps to install Microsoft Security Essentials.
5. After installation, restart your computer and open Microsoft Security Essentials.
6. On the Home tab, choose the Full scan option, and then click Scan now.

Install Windows Defender Offline Beta

Windows Defender Offline Beta is a malware tool desgined to remove hard to eliminate viruses that start before Windows boots. To use Windows Defender Offline Beta, follow the steps below:

1. On a non-infected computer,
2. Click Download the 32 bit version or Download the 64 bit version depending on which version of Windows you are running. If you're unsure of which version of Windows you are running, visit:
3. When prompted, click Save As. Save the file to a removable media source, such as a DVD, CD, or USB drive.
4. On the infected computer, insert the DVD, CD, or USB drive and restart the computer.
5. When prompted, press the key to choose boot options, such as F12, F5, or F8, depending on your BIOS.
6. Use the arrow key to scroll to the drive containg the Windows Defender Offline Beta file. The computer will start Windows Defender Offline Beta, which will immediatley start scanning for malware.

How to protect your computer against viruses

To protect your computer against viruses, follow these steps:

1. Turn on the firewall.
2. Keep your computer up-to-date.
3. Install Microsoft Security Essentials and keep it up to date.

What are rogue virus alerts?

Rogue security software programs will try to make you think that your machine is infected by a virus and usually prompt you to download and/or buy a removal product. The names of these products usually contain words like “Antivirus,” “Shield,” “Security,” Protection,” “Fixer,” so they appear to be legitimate. They will often run immediately when downloaded, or the next time your computer starts up. Rogue security software can prevent applications from opening, including Internet Explorer, and may display legitimate and very important Windows files as infections. Some typical error messages or pop ups you may receive may contain:

Warning!
Your computer is infected!
This computer is infected by spyware and adware.

A good sign that the software is not beneficial to you is that when you try to close the window it will continually pop up warnings similar to:

Are you sure you want to navigate from this page?
Your computer is infected! They can cause data lost and file corruption and need to be treated as soon as possible. Press CANCEL to prevent it. Return to System Security and download it to secure your PC.
Press OK to Continue or Cancel to stay on the current page.
It is strongly recommended that you don't download or purchase any kind of software that advertises in this manner.

How to remove rogue software

If you feel you have rogue software on your computer Microsoft has offered a number of ways to help you remove it.

Use the free Microsoft Safety Scanner
Microsoft offers a free online tool that will scan and remove potential threats from your computer. To perform the scan, visit: http://www.microsoft.com/security/scanner/

Download and install Microsoft Security Essentials

Microsoft Security Essentials is a free tool that will help prevent rogue software, viruses, and other malicious programs from installing on your computer as well as remove them. Once you have finished using the Microsoft Safety Scanner, install Microsoft Security Essentials. To do so, follow the steps below:

1. Go to the Microsoft Security Essentials site at: http://windows.microsoft.com/en-US/windows/products/security-essentials
2. Click Download Now.
3. Follow the steps in the Installation Wizard to install Microsoft Security Essentials.

Manually remove the rouge software

If the rogue software cannot be detected or removed using Microsoft Safety Scanner and/or Microsoft Security Essentials, try the steps below to locate the offending program and delete it:

1. Write down the name of the rogue software. For this example we'll call it XP Security Agent 2010.
2. Start Windows in Safe Mode with Networking:
   1. Restart your computer.
   2. When you see the computer's manufacturer's logo, press and hold the F8 key.
   3. When prompted, use the arrow keys to highlight Safe Mode with Networking and press the Enter key.
3. Click Start and check to see if the rogue software appears in the Start menu. In this case, we'll call it XP Security Agent 2010. If it's not listed there, click All Programs and scroll to find the rogue software's name.
4. Right-click the offending program, then click Properties.
5. Click the Shortcut tab.
6. In the Properties dialogue box, check the path of the rogue program listed in Target. For this example, it will appear as: C:\Program Files\ XP Security Agent 2010. Note: The folder name will often appear as a random number.
7. Click Open File Location.
8. In the Program Files window, click Program Files in the address bar.
9. Scroll until you find the offending program folder. For this example, it will be named XP Security Agent 2010.
10. Right-click the folder, then click Delete.
11. Restart your computer.
12. Go to the Microsoft Safety Scanner site at: http://www.microsoft.com/security/scanner/
13. Follow the steps to run the scan and remove the offending rogue software.