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| Symantec Security Response http://securityresponse.symantec.com |
W97M.Melissa.V | 
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W97M.Melissa.V is a modified variant of W97M.Melissa.A virus. The key changes made from the original Melissa virus are the virus module name (now called "MP?"); the email subject/message; and a malicious payload, which deletes some files. Please refer to the W97M.Melissa.A for more general information on the Melissa virus.
| Also Known As: | W97M.Melissa.A, W97M.Melissa.Variant |
| Type: | Macro, Worm |
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- Payload Trigger: Opening or closing infected documents
- Payload:
- Large scale e-mailing: Attemps to mail itself to up to 40 entries in the Outlook address book
- Modifies files: Delete files from the root directory of drives F, H, I, L, M, N, O, P, Q, S, X, and Z
- Subject of email: My pictures USERNAME
- Target of infection: Word documents and the normal template
As its primary payload, the virus attempts to use Microsoft Outlook to email a copy of the infected document to up to 40 other people. When a user opens or closes an infected document, the virus first checks to see if it has done this mass emailing once before by checking the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\ with an "MP?" value.
If this key has a value "MP" set to the value "...by 22" then the mass emailing has been done previously from the current machine. The virus will not attempt to do the mass mailing a second time if it has already been done from this machine.
If it does not find the registry entry, it will do the email payload just like W97M.Melissa.A. The difference is that it only sends to up to 40 addresses, the subject line is "My Pictures USERNAME" where USERNAME is taken from a Microsoft Word setting, and the email message is now blank.
The second payload now replaces the currently selected text of the document with:
- Opening Microsoft Outlook...
Hint: Get Norton 2000 not McAfee 4.02
It also displays a message box with the following message:
Please Check Your OutLook Inbox E-Mail!
This variant also has a malicious payload that attempts to delete files from the root directory of drives F, H, I, L, M, N, O, P, Q, S, X, and Z.
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.
The additional Windows Registry value presents no harm. In fact, if it's already set to "by 22", it will prevent the mass emailing. If you'd like, you can easily remove this registry value using Windows REGEDIT utility.
Write-up by: Raul Elnitiarta