TROJ_CLARETOR.AM

 Analysis by: Abraham Latimer Camba

 ALIASES:

Trojan:Win32/Claretore.gen!A (Microsoft), W32/Proxyier.A!tr.bdr (Fortinet), Gen:Variant.Kazy.62909 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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 is injected into all running processes to remain memory resident.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

65,024 bytes

File Type:

EXE, DLL

Memory Resident:

Yes

Initial Samples Received Date:

30 Mar 2012

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:

  • %User Temp%\{random hexadecimal number}-{random digit}.tmp
  • %User Profile%\{random hexadecimal number}-{random digit}.exe

(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.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It is injected into all running processes to remain memory resident.

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Update Server = "%User Profile%\{random hexadecimal number}-{random digit}.exe"

Other Details

This Trojan deletes the initially executed copy of itself

NOTES:

It monitors the network activity of the processes it hooks. It looks for the strings google-analytics.com/ga.js and www.google-analytics.com/ga.js. If found, it replaces them with {BLOCKED}xscanner89.com/ga.js.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

8.874.04

FIRST VSAPI PATTERN DATE:

30 Mar 2012

VSAPI OPR PATTERN File:

8.875.00

VSAPI OPR PATTERN Date:

31 Mar 2012

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

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Update Server = "%User Profile%\{random hexadecimal number}-{random digit}.exe"

Step 4

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