JBellz

Classification

Malware

Trojan

W32

JBellz, Trojan.Linux.JBellz

Summary

JBells is a trojan embedded into malformed MP3 files. The trojan uses a vulnerability in mpg123 which is a command-line MP3 player for Linux and other *NIX systems. When the trojanized MP3 is played with a vulnerable version of mpg123 a routine is started that deletes the current user's home directory and it's content.

The latest development version of mpg123 (0.59s) was tested and found to be vulnerable to this attack, while the latest stable version (0.59r) is not vulnerable.

The original exploit code generates ready to distribute trojanized MP3s for Suse 8.0 and Slackware 8.0 distributions.

Removal

Automatic action

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.

Suspect a file is incorrectly detected (a False Positive)?

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 detection database 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.

Find out more

Knowledge Base

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User Guide

See the user guide for your product on the Help Center.

Contact Support

Chat with or call an expert for help.

Submit a sample

Submit a file or URL for further analysis.

Technical Details

The exploit code generates an MP3 file with malformed header that causes a buffer overflow in mpg123's header parsing code. The malicious buffer is constructed so that it calls a command shell with a one-line command that removes the user's home directory recursively.

Even though the original exploit contains settings for the distributions mentioned above it is unfortunately easy to modify the exploit code to affect other Linux distributions and versions as well. Because of this users of vulnerable mpg123 versions are advised to change their mpg123 to a non-vulnerable version, regardless of their distribution.