Analysis by: Nikko Tamana

 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: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: 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 executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 11,952 bytes
File Type: Java Class
Memory Resident: Yes
Initial Samples Received Date: 16 May 2013
Payload: Connects to URLs/IPs

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.

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
JAVA = ""%Program Files%\Java\jre6\bin\javaw.exe" -jar "%User Temp%\a.gif""

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://xxx3.{BLOCKED}a.info/a.gif
  • http://xxx3.{BLOCKED}a.info/{file name}.txt

It saves the files it downloads using the following names:

  • %User Temp%\a.gif - also detected as JAVA_BANKER.ZIP
  • %User Temp%\update.gif - non-malicious file

(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.)

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Other Details

This Trojan executes the downloaded file using the following commands:

  • cmd /c attrib +h %User Temp%\a.gif

(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.)

NOTES:

The file this malware downloads depends on the Windows operating system version of the affected computer. The downloaded file is a non-malicious component used by Windows in remote desktop connections. The file {variable file name} can be any of the following:

  • 764-7600.txt - if operating system is Windows 7 64-bit for enterprise
  • 764.txt - if operating system is Windows 7 64-bit for non-enterprise
  • 732-7600.txt - if operating system is Windows 7 32-bit for enterprise
  • 732.txt - if operating system is Windows 7 32-bit non-enterprise
  • xp.txt - if operating system is other than Windows 7

This malware determines the Windows operating system version installed in the affected machine by executing this command line:

cmd.exe /C ver

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.922.05
FIRST VSAPI PATTERN DATE: 16 May 2013
VSAPI OPR PATTERN File: 9.923.00
VSAPI OPR PATTERN Date: 16 May 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 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
    • JAVA = ""%Program Files%\Java\jre6\bin\javaw.exe" -jar "%User Temp%\a.gif""

Step 4

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\a.gif
  • %User Temp%\update.gif

Step 5

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