This page shows details and results of our analysis on the malware W97M/Melissa.u

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Threat Detail

  • Malware Type: Virus
  • Malware Sub-type: Macro
  • Protection Added: 1999-10-08

This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.

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Malware Proliferation

This virus is a modified variant of the W97M/Melissa.a virus. There are minor changes which differentiate this from it's obvious clone parent. The module name is "Mmmmmmm" instead of "Melissa" however this virus does use MAPI email client to send a copy of itself to the first 4 available recipients in the address book. As with the first version of this virus, macro security settings in Word2000 are minimized by a registry modification.

Email messages with this virus attached will arrive with the subject line "pictures " followed by the registered name used for the local installation of Word97 or Word2000 that the email was sent from. The body of the message is "what's up ?". After the local machine is infected and the email has been sent, this virus has a damaging payload which includes the deletion of several system files. The deletion is made possible by first using the installed ATTRIB tool to remove read-only, hidden and system attributes to files, then issuing a delete instruction on them. The following is a list of files attempted removed from computers which receive and execute this virus:

c:\     <- being zealous proves typos can happen even for virus writers

Infected documents will have the following line of text inserted into the active document ">>>>>Please Check Outlook Inbox Mail<<<<<". It should be noted that the damaging payload will occur each time the infection routine is run, which in documents is during the system event of opening a document. The global template contains a subroutine named "Document_Close" while documents contain a routine named "Document_Open".

This virus can be detected by VirusScan engine v4.0.35 and DAT files of at least 4020 when using heuristic scanning method as "virus or variant of W97M/Melissa.gen".

Macro warning if opening infected document, increase in size to global template, confirmation of changes to NORMAL.DOT. Removal of system files listed above; complaint by other users of receiving email from you with the above listed characteristics.

Opening infected documents will infect global template

EXTRA Drivers
VirusScan 4 with the 4.0.25 engine (and above).
Dr. Solomon's AVTK 7.95 and above.

All Users :
Script,Batch,Macro and non memory-resident:
Use current engine and DAT files for detection and removal.

PE,Trojan,Internet Worm and memory resident :
Use specified engine and DAT files for detection. To remove, boot to MS-DOS mode or use a boot diskette and use the command line scanner:


Additional Windows ME/XP removal considerations

Users should not trust file icons, particularly when receiving files from others via P2P clients, IRC, email or other mediums where users can share files.

AVERT Recommended Updates :

* Office2000 Updates

* Malformed Word Document Could Enable Macro to Run Automatically (Information/Patch )

* scriptlet.typelib/Eyedog vulnerability patch

* Outlook as an email attachment security update

* Exchange 5.5 post SP3 Information Store Patch 5.5.2652.42 - this patch corrects detection issues with GroupShield

For a list of attachments blocked by the Outlook patch and a general FAQ, visit this link .
Additionally, Network Administrators can configure this update using an available tool - visit this link for more information .

It is very common for macro viruses to disable options within Office applications for example in Word, the macro protection warning commonly is disabled. After cleaning macro viruses, ensure that your previously set options are again enabled.