X97M.Sugar

SUMMARY

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.

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

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

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.

While infecting a worksheet, this macro virus creates a randomly named temporary text file. The virus uses the username (as set in Tools-Options-General) for the file name. For example, if the username is set to "John Smith", it creates "C:John Smith" temporary file.

This macro virus also creates a "BOOK1." file in MS Excel startup directory (usually OfficeXLSTART). By putting "BOOK1." in MS Excel startup directory, the viral code always gets loaded when MS Excel starts.

If the virus finds user VBA module(s) while infecting, it adds an Auto_Close subfunction into the user module(s). This subfunction re-inserts the viral code into "ThisWorkbook" from the temporary text file. If it can not find the temporary text file, it displays the following message:

"Why Did You Remove Sugar.Poppy?"

The virus also disables the Macro virus protection in MS Excel. To achieve this, the virus strangely takes a very indirect way. It adds an AutoExec macro in MS Word and executes it. The AutoExec macro disables MS Excel Macro Virus Protection 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.