X97M.Laroux.KV

SUMMARY

This is a standard Excel macro virus that spreads its infection when an infected spreadsheet is opened or saved. This virus adds Visual Basic Application (VBA) module into an infected spreadsheet. and adds its viral code into everyworksheet in the spreadsheet file.

Protection

• Virus Definitions (Intelligent Updater) May 23, 2000

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: It drops a viral PERSONAL.XLS

Distribution

• Distribution Level: Low
• Target of Infection: MS Excel Spreadsheets

TECHNICAL DETAILS

This MS Excel 97 macro virus adds Visual Basic Application (VBA) module into an infected spreadsheet. This macro virus adds its viral code into every worksheet in the spreadsheet file.

The infection routine gets triggered on activation or deactivation of an infected worksheet while editing in MS Excel. A worksheet is active when it is being edit. An active worksheet gets deactivated when a user edits another worksheet window.

This macro virus also creates a "Personal.xls" file is normally in MS Excel startup directory (usually OfficeXLSTART). By putting "Personal.xls" in MS Excel startup directory, the viral code always gets loaded when MS Excel starts.

The virus also disables the Macro virus protection in MS Excel.The disabling of the MS Excel Macro Virus Protection is achieved in the viral code by clearing the value in Windows Registry. With these options disabled, MS Excel 97 does not warn or prompt while opening a spreadsheet with macro in it.

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

Norton AntiVirus can remove the virus from any infected spreadsheets. It is also safe to delete the Personal.xls file in the Xlstart directory.

The disabled options can be restored from Tools-Option menu.