Analysis by: Jennifer Gumban
 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via network shares, Downloaded from the Internet

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.

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 532,992 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Aug 2012
Payload: Corrupts hard disk, Deletes files

Arrival Details

This worm may arrive via network shares.

It 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 copies of itself into the affected system and executes them:

  • %System%\trksrv.exe

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It drops and executes the following files:

  • %System%\netinit.exe ← used for reporting (damaged)
  • %System%\{random filename}.exe ← used to wipe MBR (WORM64_DISTTRACK.SM)
      where {random filename} is any of the following:
    • caclsrv
    • certutl
    • clean
    • ctrl
    • dfrag
    • dnslookup
    • dvdquery
    • event
    • findfile
    • gpget
    • ipsecure
    • iissrv
    • msinit
    • ntfrsutil
    • ntdsutl
    • power
    • rdsadmin
    • regsys
    • sigver
    • routeman
    • rrasrv
    • sacses
    • sfmsc
    • smbinit
    • wcscript
    • ntnw
    • netx
    • fsutl
    • extract

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Propagation

This worm drops copies of itself in the following shared folders:

  • ADMIN$
  • C$\WINDOWS
  • D$\WINDOWS
  • E$\WINDOWS

Dropping Routine

This worm executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

Other Details

This worm adds and runs the following services:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
ImagePath = "{malware path and filename}"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
DisplayName = "Distributed Link Tracking Server"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
DependOnService = "RpcSs"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
DependOnGroup = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
Description = "Enables the Distributed Link Tracking Client service within the same domain to provide more reliable and efficient maintenance of links within the domain. If this service is disabled, any services that explicitly depend on it will fail to start."

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\LanmanWorkstation
DependOnGroup = "0"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\LanmanWorkstation
DependOnService = "TrkSvr"

NOTES:

It creates the file %Windows%\inf\netft429.pnf. The said file contains the number of files to be compromised. It is used for reporting to its C&C server.

The 'netinit.exe' is responsible for the following:

  • Sending information about the infection back to the server.
  • It is capable of receiving files from the remote server and execute it on the affected system.

    •   SOLUTION

    Minimum Scan Engine: 9.800

    Step 1

    Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

    Step 2

    Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

    Step 3

    Restart in Safe Mode

    [ Learn More ]

    Step 4

    Delete this registry key

    [ Learn More ]

    =Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
      • TrkSvr

    Step 5

    Delete these registry values

    [ Learn More ]

    Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

     
    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation
      • DependOnGroup = ""
    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation
      • DependOnService = TrkSvr

    Step 6

    Search and delete these files

    [ Learn More ]
    There may be some 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.
    %Temp%\key8854321.pub
    %System%\Drivers\drdisk.sys
    %Windows%\inf\netimm173.pnf

    Step 7

    Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM64_DISTTRACK.SMA. 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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