Analysis by: Merianne Polintan
ALIASES:

DDoS:Win32/Nitol.B(Microsoft),Trojan.Win32.Generic.pak!cobra(Sunbelt),a variant of Win32/Agent.PKI trojan(NOD32),Gen:Trojan.Heur.cqW@yP6MwDe(Bitdefender)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 43,008 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 24 Apr 2013

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system and executes them:

  • %Windows%\{Random File Name}.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

It drops the following copies of itself into the affected system:

  • %User Temp%\{Random Characters}

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Enum\Root\LEGACY_WINHELP32

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager
PendingFileRenameOperations = "%User Temp%\{Random Characters}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\WinHelp32
ImagePath = "%Windows%\{Random File Name}.exe"

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}otaek.no-ip.org

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.876.07
FIRST VSAPI PATTERN DATE: 24 Apr 2013
VSAPI OPR PATTERN File: 9.877.00
VSAPI OPR PATTERN Date: 25 Apr 2013

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

Restart in Safe Mode

[ Learn More ]

Step 3

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\ControlSet001\Enum\Root
    • LEGACY_WINHELP32

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\SYSTEM\ControlSet001\Services\WinHelp32
    • ImagePath = "%Windows%\{Random File Name}.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager
    • PendingFileRenameOperations = "%User Temp%\{Random Characters}"

Step 5

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