Analysis by: Sabrina Lei Sioting
ALIASES:

TrojanDropper:Win32/Farfli.E (Microsoft), Packed.Win32.Klone.d (Kaspersky), Trojan.Malcol (Symantec), Trojan.Win32.Packer.Klone.d (Sunbelt), W32/Zegost.AB.gen!Eldorado (Fprot),

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 71,680 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 07 Jul 2012

Arrival Details

This backdoor 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 backdoor drops the following files:

  • %Program Files%\Oklm\welmnopqr.jpg

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

It creates the following folders:

  • %Program Files%\Oklm

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\306319159
ImagePath = "%System%\svchost.exe -k imgsvc"

HKEY_LOCAL_MACHINE\SOFTWARE\306319159
DisplayName = "welmno Qrstuvwx Abcdefgh Jklm"

HKEY_LOCAL_MACHINE\SOFTWARE\306319159\
Parameters
ServiceDll = "%Program Files%\Oklm\welmnopqr.jpg"

HKEY_LOCAL_MACHINE\SOFTWARE\306319159\
Parameters
ServiceMain = "DarkAngel"

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\
Enum\Root\LEGACY_REMOTEACCESS

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_WELMNO_QRSTUVWX_ABC

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\welmno Qrstuvwx Abc

HKEY_LOCAL_MACHINE\SOFTWARE\287397126

HKEY_LOCAL_MACHINE\SOFTWARE\306319159

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Tracing\Router

Other Details

This backdoor connects to the following possibly malicious URL:

  • xzz5060.{BLOCKED}6.org

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.200

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

Restart in Safe Mode

[ Learn More ]

Step 3

Restart in Safe Mode, and then 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.

Step 4

Search and delete these folders

[ 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.
  • %Program Files%\Oklm

Step 5

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