TROJ_KRYPTIK.BMZ

October 08, 2012
 Analysis by: Michael Cabel
 ALIASES:

Kaspersky: Trojan.Win32.Pirminay.cyp

 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.

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

346,544 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

16 Feb 2011

Payload:

Drops 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 and executes the following files:

  • %System%\{random file name}.exe - detected as TROJ_FAM_00001e3.TOMA

(Note: %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.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\{random registry key}

HKEY_LOCAL_MACHINE\SOFTWARE\{random registry key}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{Random Characters} = "%System%\{Random File Name}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
6 = {random values}

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
9 = {random values}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
6 = {random values}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
9 = {random values}

Dropping Routine

This Trojan drops the following files:

  • %System Root%\Documents and Settings\{user name}xplore.exe

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

Download Routine

This Trojan connects to the following malicious URLs:

  • http://{BLOCKED}ut4.cn/update/utu.dat

As of this writing, the said sites are inaccessible.

HOSTS File Modification

This Trojan adds the following strings to the Windows HOSTS file:

  • 127.0.0.1 thepiratebay.org
  • 127.0.0.1 www.thepiratebay.org
  • 127.0.0.1 mininova.org
  • 127.0.0.1 www.mininova.org
  • 127.0.0.1 forum.mininova.org
  • 127.0.0.1 blog.mininova.org
  • 127.0.0.1 suprbay.org
  • 127.0.0.1 www.suprbay.org

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

7.841.50

VSAPI PATTERN Date:

16 Feb 2011

VSAPI PATTERN Date:

2/16/2011 12:00:00 AM

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

Remove malware files dropped/downloaded by TROJ_KRYPTIK.BMZ

    • TROJ_FAM_00001e3.TOMA

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\Internet Settings
    • 6 = {random values}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • 9 = {random values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • 6 = {random values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • 9 = {random values}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {Random Characters} = %System%\{Random File Name}.exe

Step 4

Remove these strings added by the malware/grayware/spyware in the HOSTS file

[ Learn More ]
    127.0.0.1       thepiratebay.org
    127.0.0.1       www.thepiratebay.org
    127.0.0.1       mininova.org
    127.0.0.1       www.mininova.org
    127.0.0.1       forum.mininova.org
    127.0.0.1       blog.mininova.org
    127.0.0.1       suprbay.org
    127.0.0.1       www.suprbay.org
"

Step 5

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