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WORM_KOOBFACE.AV
Aliases: Trojan.Win32.Jorik.Koobface.bd (Kaspersky); TrojanDownloader:Win32/Utagent.A (Microsoft)
Malware type: Worm
Destructive: No
Platform: Windows 2000, Windows XP, Windows Server 2003
Encrypted: Yes
In the wild: Yes

Overview


Upon execution, this worm sends an HTTP request to its C&C to download a file.

It saves the downloaded file as %Current%\123.tmp, which contains a download link of a torrent file pointing to a Trojanized software. It then uses its dropped uTorrent client to silently download the referenced Trojanized software, leading to the download of several components.

As of writing, the downloaded files are detected as follows:

  • TROJ_SPAMMER.AA

  • WORM_KOOBFACE.AV

  • WORM_KOOBFACE.FE

  • WORM_KOOBFACE.FH

  • WORM_KOOBFACE.FI

  • WORM_KOOBFACE.FK

  • WORM_KOOBFACE.MJ

  • WORM_KOOBFACE.MM

It then executes the downloaded files. As a result, malicious routines of downloaded files are exhibited on the system.

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Technical Details


File size: Varies
Memory resident: Yes
Initial samples received date: 16 Aug 2011
Payload: Downloads files

Arrival Details

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops the following non-malicious file:

  • %User Temp%\iexplore.exe - uTorrent client
  • %Current%\123.tmp - non-malicious component

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
trr = {malware path and file name}

NOTES:

Upon execution, it sends the following HTTP request to its C&C to download a file:

  • http://{C&C}/?action=torgen&v={parameter}s&a=get_tfile

The C&C server may be any of the following:

  • {BLOCKED}jkvhhfhflkfiuhieufhieu.com
  • {BLOCKED}0jg9glkdnbo43ighbjemh6.com
  • {BLOCKED}b49tkfnbk3r0ei5m539tjg.com
  • {BLOCKED}0934340tnvnwnv490g9405.com
  • {BLOCKED}djcncfjkdfikcndcfndfjcjcfkj.com
  • {BLOCKED}fhdskvfjdshfjhfjsahfkjfsajk.com
  • {BLOCKED}38sj3n5nt659dl2395k59f.com
  • {BLOCKED}bfk2948sk3n5b659259887.com
  • {BLOCKED}4k2bf9305k67hb20305696.com
  • {BLOCKED}pdjsakcndsjkcbdskjcbdsecjds.com
  • {BLOCKED}ndbajxnbndjdkjdokcn827nnnsk.com
  • {BLOCKED}wddcjbsjdwdjwopdwojdjjjjjjw.com
  • {BLOCKED}fvnw0f38hn09fjnlsn2r9v.com
  • {BLOCKED}vxsdhduhdhcbdxhdshcxdhgxdcd.com
  • {BLOCKED}5693038f73h50658395020.com
  • {BLOCKED}jwqdsajnsjndnsncdsnmcccfasw.com
  • {BLOCKED}wdfhsaubxxdwijdididhdhjhdhw.com
  • {BLOCKED}xbndskjdsldlodfjcfnapskdjdc.com
  • {BLOCKED}bdjduchncdfjhdfujdjddsxbshb.com
  • {BLOCKED}bdjduchncdfjhdfujdjddsxbshb.com

It saves the downloaded file as %Current%\123.tmp, which contains a download link of a torrent file pointing to a Trojanized software. It then uses its dropped uTorrent client to silently download the referenced Trojanized software, leading to the download of the following components:

  • %User Temp%\{file name of downloaded torrent}\setup.exe – decrypts and executes setup3.cab; executes setup2.cab (also detected as WORM_KOOBFACE.AV)
  • %User Temp%\{file name of downloaded torrent}\setup1.cab – downloader of other component binaries (also detected as WORM_KOOBFACE.AV)
  • %User Temp%\{file name of downloaded torrent}\setup2.cab – actual installer of the intended software
  • %User Temp%\{file name of downloaded torrent}\setup3.cab – decrypts and executes setup1.cab (also detected as WORM_KOOBFACE.AV)

The component setup1.cab then performs the following HTTP request to the C&C to download a dynamic list of component download sites:

  • http://{C&C}/.sys.php?action=ldtor&v=1&a={parameter}&id={parameter}&hardid={parameter}
  • http://{C&C}/.sys.php?action=fbgen&v=1

It also saves the downloaded list as %Current%\123.tmp.

The downloaded components are all saved using the file name %User Temp%\tx{character}.tmp. As of writing, the downloaded files are detected as follows:

  • TROJ_SPAMMER.AA
  • WORM_KOOBFACE.AV
  • WORM_KOOBFACE.FE
  • WORM_KOOBFACE.FH
  • WORM_KOOBFACE.FI
  • WORM_KOOBFACE.FK
  • WORM_KOOBFACE.MJ
  • WORM_KOOBFACE.MM

It then executes the downloaded files. As a result, malicious routines of downloaded files are exhibited on the system.

Solution


Minimum scan engine: 8.900
First VSAPI Pattern File: 8.360.02
First VSAPI Pattern Release Date: 17 Aug 2011

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by WORM_KOOBFACE.AV

     TROJ_SPAMMER.AA
    WORM_KOOBFACE.AV
    WORM_KOOBFACE.FE
    WORM_KOOBFACE.FH
    WORM_KOOBFACE.FI
    WORM_KOOBFACE.FK
    WORM_KOOBFACE.MJ
    WORM_KOOBFACE.MM

Step 3

Identify and terminate files detected as WORM_KOOBFACE.AV

[ Learn more ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Delete this registry value

[ Learn more ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.


  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • trr = {malware path and file name}

Step 5

Search and delete this folder

[ Learn more ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
%User Temp%\{file name of downloaded torrent}

Step 6

Search and delete these files

[ Learn more ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
%Current%\123.tmp
%User Temp%\iexplore.exe

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_KOOBFACE.AV. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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Analysis By: Roland Marco Dela Paz

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