Trojan-Downloader:W32/Mebroot.gen!B

Threat description

Details

CATEGORYMalware
TYPETrojan-Downloader

Summary

Trojan-Downloader:W32/Mebroot.gen!B is a Generic Detection that identifies the downloader program responsible for fetching the installer for the Mebroot rootkit.



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.

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Technical Details

This malware is discussed in further detail in the following Labs Weblog posts:

The downloader is known to be distributed to users via a malicious website (driveby download) or via an exploit.

Activity

When active, the downloader downloads an encrypted file on port 443 or 80 from:

  • http://bcoxgcgxes.com (encrypted file)

where (encrypted file) is a defined string. This string is unique in every sample.

Once downloaded, the encrypted file is first saved in an allocated memory where it will be decrypted, then saved to a file in a temporary folder. The file will then be executed.

The encrypted file is encrypted with an RC2 encryption algorithm. The Cipher Hash that is used in the decryption is based on a defined string that is also unique in every sample.

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