Scalper, Unix/Scalper, Ehchapa, PHP/Exploit-Apache, UNIX/Exploit-Apache, Exploit.Linux.Apache.134, Hacktool.Echapa, Scalper.A, Unix/Scalper.A


Scalper affects systems running FreeBSD running the vulnerable version of Apache web server.

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.

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Submit a sample

Submit a file or URL for further analysis.

Technical Details

Scalper is a worm that propagates from a FreeBSD system to another via a security vulnerability in Apache web server, known as chunked encoding vulnerability.

At the time of writing, F-Secure have not received any direct reports about infected systems from the field.

If the worm gains access to the server, it creates a temporary file "/tmp/.uua", which is an uuencoded worm. This file is decoded to "/tmp/.a" and executed. The uuencoded file is removed.

At this point the worm sets up a backdoor to UDP port 2001 and starts scanning predefined set of Class-A networks. If the worm finds a web server, it checks if the server is running Apache, and if so, it will attempt to infect it. While the exploit code that Scalper uses will only infect systems running FreeBSD, these attempts will be visible in Apache servers running on other platforms as well.

The backdoor component of the worm allows a remote control of the worm, sending of email, uploading of files and executing of arbitary programs. The execution of programs happens with the same user privilege as the Apache server. The backdoor can also perform different kind of denial of service attacks against arbitary hosts.

The worm does not modify the system configuration, and it is visible in the system process list as a process ".a".

Scalper can be removed from the system by deleting file "/tmp/.a" and terminating the worm process with command "killall -9 .a".

The vulnerability used by the worm is fixed in Apache server versions 1.3.26 and 2.0.39. Further information is available from:

Apache Sofware Foundation: