Summary
Gismor is a mass-mailing worm that arrives in email 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
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
Check for the latest database updates
First, check if your F-Secure security program is using the latest updates, then try scanning the file again.
Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
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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