Korgo.H

Classification

Malware

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Korgo.H, Worm.Win32.Padobot.gen, W32/Korgo.worm.n, WORM_KORGO.H

Summary

This Korgo (aka Padobot) variant was found in the beginning of June, 2004. It is very similar to the previous Korgo variants. It spreads throughout the Internet using a vulnerability in Microsoft Windows LSASS. A description of the vulnerability can be found in Microsoft Security Bulletin MS04-011: https://www.microsoft.com/technet/security/bulletin/MS04-011.mspx

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

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User Guide

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Submit a sample

Submit a file or URL for further analysis.

Technical Details

The worm's file is a PE executable 10752 bytes long packed with UPX file compressor. The unpacked file's size is about 18 kilobytes.

When the worm's file is run, it first deletes the FTPUPD.EXE file. Then the worm creates a mutex with the "uterm11" name. This is done to avoid loading multiple copies of the worm into memory.

Next, the worm deletes Registry key values and terminates processes with any of the following names:

  • Windows Security Manager
  • Disk Defragmenter
  • System Restore Service
  • Bot Loader
  • SysTray
  • WinUpdate
  • Windows Update Service
  • avserve.exe
  • avserve2.exeUpdate Service

The key values are deleted from the following Registry key:

  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]

After that the worm installs itself to system and creates a startup key for its file in the Registry. The worm's file is copied to Windows System folder with a randomly generated name. The following Registry key is then created:

  • [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
  • "Windows Update" = "%WinSysDir%\<random>.exe"

where WinSysDir represents Windows System directory name and <random> represents random characters. The name of the worm's file can be for example 'jsoxse.exe'.

Additionally the worm can create the following Registry key:

  • [HKLM\Software\Microsoft\Wireless]
  • "Client" = "1"

The worm tries to start its spreading routine as a remote thread of Windows Explorer. If this fails, the worm starts the spreading thread directly.

Being active, the worm starts the IDENT server on TCP port 113. It also listens on TCP port 3067. Through this port the worm can download files to Windows System folder and run them. However, before that a secure authentication takes place so unauthorised clients are not allowed to upload and run files. Additionally the worm can listen on random TCP ports.

The worm spreads to remote computers using LSASS vulnerability. It contacts remote computers on TCP port 445, exploits the vulnerability and copies its file to a remote system.

The worm tries to contact the following IRC servers on port 6667:

  • moscow-advokat.ru
  • graz.at.eu.undernet.org
  • flanders.be.eu.undernet.org
  • caen.fr.eu.undernet.org
  • brussels.be.eu.undernet.org
  • los-angeles.ca.us.undernet.org
  • washington.dc.us.undernet.org
  • london.uk.eu.undernet.org
  • irc.tsk.ru
  • lia.zanet.net
  • gaspode.zanet.org.za
  • irc.kar.net

If connection is successful, the worm joins the #taty channel and creates a bot with a random name there.