VBS.Lanus.gen

SUMMARY

VBS.Lanus.gen is an encoded Visual Basic script (VBS) contained within a .htm or .html page. This script is viral, and when executed it infects .htm and .html files by appending itself to the end of the file. For the script to activate, you must have the Windows Scripting Host 5.1 or later installed and allow the ActiveX controls to run when the infected .htm or .html page is viewed.

Protection

• Virus Definitions (Intelligent Updater) June 7, 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
• Modifies Files: .htm and .html

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

An infected Web page contains the encoded Visual Basic script at the end of the file. If the page is viewed, it displays itself normally, and there is a random chance the viral script will execute. When it does, it first prompts you to allow its ActiveX controls to run. If you allow this, the script searches the drive and infects .htm and .html files found in the following locations:

• The root folder of the drive
• The WindowsHelp folder and its subfolders
• The WindowsSystem folder and its subfolders
• The WindowsTemp folder and its subfolders
• The Desktop folder and its subfolders
• The Desktop folder attributed to AllUsers and its subfolders

The script performs a check to verify whether it has already infected .htm and .html files. If it has already infected a file in a particular folder, it will not infect newer .htm or .html files present in that same folder. This holds true if the script is executed more than once.

The script requires that the Windows Scripting Host 5.1 or later be installed.

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

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. Files detected as infected by VBS.Lanus.gen should be deleted and restored from backup if necessary.