Threat Encyclopedia

TROJ_KRYPTIK.BMP

Publish date: January 14, 2013

ANALYSIS BY

Michael Cabel


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, Dropped by other malware


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 connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

TECHNICAL DETAILS

File Size:

10,240 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Jan 2012

Payload:

Downloads files

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%\label.exe
  • %User Temp%\ethnet.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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

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
IEHelpService = "%User Temp%\label.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MsUpdate = %User Temp%\ethnet.exe

Download Routine

This Trojan accesses the following websites to download files:

  • http://www.{BLOCKED}mb.com.tw/image.bmp

It saves the files it downloads using the following names:

  • %User Temp%\{Random Characters}.bmp

(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.)

Trend Micro detects the dowloaded file as:

  • TROJ_KRYPTIK.BMP

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{BLOCKED}.{BLOCKED}.207.84/ms.htm?id={Random}
  • http://{BLOCKED}.{BLOCKED}.207.84:53/ms.htm?id={Random}
  • http://{BLOCKED}.{BLOCKED}.157.251/ms.htm?id={Random}

However, as of this writing, the said sites are inaccessible.

NOTES:

It decrypts the downloaded file and the encrypted file is saved as %User Temp%\{Random Characters}.tmp.

SOLUTION

Minimum Scan Engine:

9.300

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

Scan your computer with your Trend Micro product and note files detected as TROJ_KRYPTIK.BMP

Step 3

Terminate a process file/s detected as TROJ_KRYPTIK.BMP

[ Learn More ]

*Note: If the detected file/s is/are not displayed in theWindows Task Manager, continue doing the next steps.


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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • IEHelpService = "%User Temp%\label.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • MsUpdate = %User Temp%\ethnet.exe

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_KRYPTIK.BMP. 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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