Analysis by: Kathleen Notario
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  TECHNICAL DETAILS

File Size: 96,256 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 11 Aug 2010
Payload: Drops files

Installation

This Trojan adds the following folders:

  • %Windows%\efee3f32f

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

Autostart Technique

This Trojan modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = %System%\userinit.exe,%Windows%\svchost32.exe,

(Note: The default value data of the said registry entry is %System%\userinit.exe,.)

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Network
PID = {Computer name}_{Random numbers}

Dropping Routine

This Trojan drops the following files:

  • %Windows%\efee3f32f\brrve.nls
  • %Windows%\efee3f32f\wrfsf.nls
  • %Windows%\svchost32.exe - also detected as TSPY_ZBOT.TAH

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

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI OPR PATTERN File: 7.376.17
VSAPI OPR PATTERN Date: 12 Aug 2010

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

Identify and delete files detected as TSPY_ZBOT.TAH using the Recovery Console

[ Learn More ]

Step 3

Restore this modified 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 NT\CurrentVersion\Winlogon
    • From: Userinit=%System%\userinit.exe,%Windows%\svchost32.exe,
      To: %System%\userinit.exe,

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\WindowsNT\CurrentVersion\Network
    • PID={Computer name}_{Random numbers}

Step 5

Scan your computer with your Trend Micro product to delete files detected as TSPY_ZBOT.TAH. 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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