W95.SchoolGirl.910

SUMMARY

W95.SchoolGirl.910 is a Windows virus that replicates only under Windows 95/98/Me. If it is activated under Windows NT/2000/XP, the virus does nothing but transfer control to the original host program.

This virus infects all .exe, .ocx and .scr files that it finds on all local drives (including mapped drives). Due to the way this virus infects files, it may damage or corrupt self-extracting executables and setup programs (such as InstallShield).

This virus also carries two payloads:

• Payload one:
  This payload becomes active on the 16th of every month. It simply opens up the home page for the Sichuan University of Science and Technology in China.
• Payload two:
  This payload is activated only if the year is 2002 or later and only if the day of the month is the 17th. Once activated this payload deletes all executables on all local drives (including mapped drives).

Protection

• Virus Definitions (Intelligent Updater) December 5, 2001

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Medium
• Payload Trigger: 16th of every month as well as the 17th of every month if the year is 2002 or above
• Payload: Opens the homepage of a university in your browser on the 16th of every month.
• Deletes Files: On the 17th of every month if the year is 2002 or above.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

This virus is fairly destructive, mostly due to bad programming. When this virus infects a file it may overwrite any overlays or appended data that belong to the host file. This is most likely to corrupt setup programs. Aside from this corruption this virus always increases the size of the infected file by 910 bytes, but this block will almost always be filled with junk.

Strings
This virus contains the following text string in its body:

Beautiful School Ver4.0 By Who Hooks Girl?

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

To remove this virus:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. If any files are detected as infected by W95.SchoolGirl.910, click Repair.
5. Because the infection process can corrupt certain files, after repairing the virus replace from a known clean backup any file that shows erratic behavior.