Analysis by: Kathleen Notario
 Modified by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

  TECHNICAL DETAILS

File Size: 33,792 bytes
Memory Resident: Yes
Initial Samples Received Date: 23 Aug 2011

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:

  • %System Root%\Documents and Settings\All Users\Application Data\22CC6C32.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It drops the following non-malicious file:

  • %Windows%\7C3B2A7D.exe – copy of explorer.exe
  • %System%\03014D3F.exe- copy of userinit.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

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
Shell = "%System Root%\Documents and Settings\All Users\Application Data\22CC6C32.exe"

(Note: The default value data of the said registry entry is Explorer.exe.)

NOTES:
In Windows Vista and Windows7 platform: It drops the following copy of itself:

  • %System Root%\ProgramData\22CC6C32.exe

This malware modifies the following registry entries.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
Shell = "C:\ProgramData\22CC6C32.exe"

(The default value for this entry is explorer.exe)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
Userinit = "C:\ProgramData\22CC6C32.exe"

(The default value for this entry is %System%\userinit.exe,) It replaces the following files with a copy of itself:

  • %System%\taskmgr.exe
  • %System%\userinit.exe
  • %System%\dllcache\taskmgr.exe
  • %System%\dllcache\userinit.exe

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.374.07
FIRST VSAPI PATTERN DATE: 23 Aug 2011

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 TROJ_RANSOM.AMM using either the Startup Disk or 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: Shell = "%System Root%\Documents and Settings\All Users\Application Data\22CC6C32.exe"
      To: Shell = Explorer.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "%System Root%\ProgramData\22CC6C32.exe"
      To: Shell = explorer.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit = "%System Root%\ProgramData\22CC6C32.exe"
      To: Userinit = %System%\userinit.exe,

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_RANSOM.AMM. 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.

Step 5

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %System%\taskmgr.exe
  • %System%\userinit.exe
  • %System%\dllcache\taskmgr.exe
  • %System%\dllcache\userinit.exe


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