Linux/Kork

Classification

Malware

Worm

Linux

Kork, Linux/Kork, Unix/Kork, Worm.Linux.Kork

Summary

Kork is a worm that uses the known vulnerability in lpd service to propagate from a vulnerable Linux system to another. This service is part of the default installation of Red Hat Linux 7.0.

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


Variant:Kork.A

If the worm finds a vulnerable host, it first creates two users, "kork" and "kork2", to the system without a password. "kork2" user has a root priviledge.

Kork also adds an open shell to port 666.

Next it attempts to download a trojanized login and the main part of the trojan from a web site. Since April 26th, 2001, neither of these files are available, so the worm cannot replicate any further. However, already infected machines are able to compromise other vulnerable machines by adding an open shell and users to the system.

If the download is completed, the worm installs trojanized "/bin/login" and "/bin/ps" to the system. It attemps to send sensitive system data propably to the virus writer.

Original "/bin/ps" is copied to "/usr/bin/.ps" and the original "/bin/login" is copied to "/bin/.login".

Finally the worm starts to scan random Class-B subnets for vulnerable hosts.

The vulnerability in the lpd daemon is known and already fixed within updated provided by Red Hat at: https://www.redhat.com/support/errata/rh7-errata-security.html