VBS.Blank.Gen

SUMMARY

VBS.Blank.Gen is a Visual Basic Script Trojan horse that changes the current Internet Explorer home page to the WindowsAboutBlank.htm file, which is created by the Trojan. This file contains a link to the original home page, and sends a message to a specific ICQ user through the ICQ Web pager.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (Intelligent Updater) September 25, 2001

Threat Assessment

Wild

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

Damage

• Damage Level: Low
• Payload: Resets the Internet Explorer home page

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

The script modifies the registry to set the home page for Internet Explorer to the file AboutBlank.htm. This file is created by the script in the Windows folder. AboutBlank.htm contains a link to the original Internet Explorer home page, so that it will appear that Internet Explorer has loaded the correct page when it starts. The file also automatically sends an ICQ message to a specific ICQ user whenever the home page is viewed.

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 Trojan:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
3. If any files are detected as infected by VBS.Blank.Gen, click Delete.

To reset the Internet Explorer home page:

1. Start Microsoft Internet Explorer.
2. Connect to the Internet, and go to the page that you want to set as your home page.
3. Click Tools, and click Internet Options.
4. On the General tab, under Home page, click Use Current and then click OK.