Computer Virus description, prevention and recovery

Determine if your computer is infected with a virus, worm, or Trojan, how to recover from the infection, and how to prevent future viruses.

A computer virus is an executable file that can copy itself and escape detection. Viruses may escape detection by disguising themselves as legitimate programs. Viruses are frequently rewritten and adjusted so that they are not detected. The anti-virus program must be constantly updated to find new and modified viruses.

There are at least 60,000 known viruses, and more viruses are written every day. Currently, most viruses are transmitted through emails and instant messages. Viruses often arrive with emails and pretend to be entertaining information, such as clips, music or greeting cards. Viruses may carry destructive loads, such as worms or Trojan horses.

Symptoms of viruses, worms, and Trojan horses

If you suspect or confirm that your computer is infected with a virus, obtain the latest anti-virus software. If your email or other files are infected with viruses, the following effects may occur on your computer:

Infected files may copy themselves to use up all available space on the hard disk.

Copies of infected files may be sent to all addresses in your email address list.

Virus may reformat your disk drive and delete your files and programs.

Viruses may install hidden programs, such as pirated software that can be distributed and sold from your computer.

Viruses may reduce security and allow intruders to remotely access your computer or network.

The following symptoms are generally caused by or associated with viruses:

You receive emails containing strange attachments. After the attachment is opened, a dialog box is displayed, or the system performance suddenly decreases.

Your latest attachment has a double extension name, for example, .jpg. vbs or .gif.exe.

The anti-virus program is unreasonably disabled and cannot be restarted.

The anti-virus program cannot be installed on the computer, or the installed anti-virus program cannot run.

A strange dialog box or message box appears on the screen.

Someone tells you that they recently received include additional files from you (especially the extension is. exe ,. bat ,. scr ,. vbs file), but you did not actually send it.

The new icon displayed on the desktop is not placed by you, or is not associated with any recently installed program.

A strange sound or music is unexpectedly released in the speaker.

The program disappears from the computer, but it is not intended to be uninstalled by you.
Virus Infection may also cause the following symptoms, but these symptoms may also be caused by common Windows functions, or Windows internal problems that are not caused by viruses.

Windows cannot be started at all, even if you have not made any system changes or have not installed or deleted any programs.

There are many modem activities. If an external modem is installed, you may notice that when the modem is not in use, the indicator lights will flash continuously. You may be unconsciously providing pirated software.

Windows cannot start because some critical system files are missing, and you will receive an error message listing these files.

The computer is sometimes started as scheduled, but sometimes the desktop icon and taskbar are not displayed to stop responding.

The computer runs very slowly and starts for a long time.

Even if your computer has enough RAM, there will be an error message indicating insufficient memory.

The new program cannot be installed normally.

Windows restarts unexpectedly.

In the past, normal programs often stop responding. If you try to delete or reinstall the software, the problem persists.

Scandisk and other disk utilities report multiple serious disk errors.

The partition disappears completely.

When you try to use Microsoft Office Products, the computer always stops responding.

Windows Task Manager cannot be started.

The anti-virus software indicates a virus.

Recover from virus infection and Prevent Virus Infection

To prevent virus infection or recover from virus infection, follow these steps:

Scan your computer with an updated anti-virus program.

Install the latest security patches from the Microsoft Web site.

Reinstall the anti-virus program (if it has stopped working ).
Obtain the latest "virus signature file" from the website of the anti-virus vendor ". For each type of new virus, the anti-virus vendor releases an update to deal with the new virus.

Scan your computer again to eliminate the virus.

Schedule antivirus programs to check the system while you are sleeping.

If one or more of the following conditions is true, you may have to format your computer's hard disk and reinstall Windows and all your computer programs:

The anti-virus software displays a message that cannot repair or remove viruses.

Viruses damage or delete important files on the computer. This may be the case if Windows or some programs cannot be started, or if an error message indicating file corruption or loss occurs during startup

Even after you clean up the workstation, the symptoms described in this article still exist, and you are sure the problem is caused by a virus.

Make sure that the firewall is installed on your computer. For more information about security and firewall, visit the Microsoft Web site:

For Windows XP-based computers, open the Internet Connection Firewall (ICF ).

For all other versions of Windows, install a third-party firewall.

Ensure that Microsoft Outlook Email Security Updates are installed:

By default, Outlook 2000 SP2 post-SP2 and Outlook XP SP1 include this security update.

Outlook 2000 pre-SR1 and Outlook 98 do not include this feature, but can be obtained by installing Outlook Email Security updates.

Configure Outlook Express6 to prohibit access to virus attachments.

Earlier versions of Outlook Express (pre-Outlook Express 6) do not include the attachment blocking function. Be careful when opening email attachments that do not require attachments.

Disable activity scripts in Outlook and Outlook Express.

Note: by default, activity scripts are disabled in Outlook Express 6 and Outlook 2002.