Analysis by: Christopher Daniel So
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: Yes

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Propagates via network shares

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

  TECHNICAL DETAILS

File Size: 1,978,850 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 07 Sep 2012
Payload: Drops files

Arrival Details

This worm may arrive via network shares.

Installation

This worm drops the following copies of itself into the affected system:

  • %System%\trksvr.exe

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

Autostart Technique

This worm registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
Type = "10"

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

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr
ImagePath = "%System\trksvr.exe"

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."

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\TrkSvr

Other System Modifications

This worm adds the following registry entries:

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

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

Propagation

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

  • \\{IP address}\ADMIN$\system32\{random file name}.exe
  • \\{IP address}\C$\WINDOWS\system32\{random file name}.exe
  • \\{IP address}\D$\WINDOWS\system32\{random file name}.exe
  • \\{IP address}\E$\WINDOWS\system32\{random file name}.exe

Dropping Routine

This worm drops the following files:

  • %System%\{random file name}.exe - detected by Trend Micro as TROJ_WIPMBR.DAM
  • %System%\netinit.exe - detected by Trend Micro as TROJ_DISTTRACK.DAM

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

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

NOTES:

If command-line parameters are specified, this worm drops copies of itself to the following:

  • \\{command-line parameter}\ADMIN$\system32\{random file name}.exe
  • \\{command-line parameter}\C$\WINDOWS\system32\{random file name}.exe
  • \\{command-line parameter}\D$\WINDOWS\system32\{random file name}.exe
  • \\{command-line parameter}\E$\WINDOWS\system32\{random file name}.exe

The file name indicated in {random file name} may be any of the following:

  • caclsrv
  • certutl
  • clean
  • ctrl
  • dfrag
  • dnslookup
  • dvdquery
  • event
  • extract
  • findfile
  • fsutl
  • gpget
  • iissrv
  • ipsecure
  • msinit
  • netx
  • ntdsutl
  • ntfrsutil
  • ntnw
  • power
  • rdsadmin
  • regsys
  • routeman
  • rrasrv
  • sacses
  • sfmsc
  • sigver
  • smbinit
  • wcscript

  SOLUTION

Minimum Scan Engine: 9.200

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

Remove malware/grayware files dropped/downloaded by WORM_DISTTRACK.B. (Note: Please skip this step if the threats listed below have already been removed.)

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 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\SYSTEM\CurrentControlSet\Services
    • TrkSvr

Step 5

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\SYSTEM\CurrentControlSet\Services\lanmanworkstation
    • DependOnService = "TrkSvr"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\lanmanworkstation
    • DependOnGroup = "0"

Step 6

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