Gismor

Threat description

Details

CATEGORYMalware
TYPEWorm

Summary

Gismor is a mass-mailing worm that arrives in e-mail disguised as an MP3 player program. The worm uses the the Invalid MIME Type Vulnerability to execute the infected attachment automatically when the message is opened.



Removal

Automatic action

Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for more information.

Contact Support

F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

The message that Gismor sends has the following properties:

From: MP3 Deluxe  To: My best friends  Subject: Phenomenal  

The message has no text in the body and has an attachment called 'MP3Player.exe'.

When the infected attachment is run it copies itself to Windows System Directory as 'SSMS.EXE' and adds this copy to the registry as

'HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SSMS.EXE'  

The worm uses MAPI to list all the incoming messages and sends an infected message to each sender it finds there. It uses direct SMTP connection to send the infected messages. The SMTP settings are fetched from the first active account from the user's settings. If the worm does not find the SMTP setting in the registry it uses a predefined SMTP server.

Payload

Gismor has a payload routine that overwrites certain files (.doc, .xls, .mp3, .mdb, .htm, .asp, .dbf, .cpp, .rtf, .wav) with the worm body. Based on the first analysis this routine is never called.

Notes

For more information and the fix for the Invalid MIME Type Vulnerabilty please visit

https://www.microsoft.com/windows/ie/downloads/critical/q323759ie/default.asp

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