TROJ_KRYPTK.BZ

April 25, 2014
 Analysis by: Abraham Latimer Camba
 ALIASES:

Trojan horse Delf.AOSF (AVG), Trojan.SuspectCRC (Ikarus), a variant of Win32/Kryptik.BZLQ trojan (Eset), Trojan Horse (Symantec), Trojan.Win32.Generic!BT (Sunbelt)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan deletes itself after execution.

  TECHNICAL DETAILS

File Size:

110,592 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 Apr 2014

Installation

This Trojan drops the following files:

  • %User Temp%\{random folder name 1}\{random folder name 2}\wow.dll
  • %User Temp%\{random folder name 1}\{random folder name 2}\wow.ini
  • %User Temp%\{random folder name 1}\{random folder name 2}\tmpB.tmp

(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 creates the following folders:

  • %User Temp%\{random folder name 1}
  • %User Temp%\{random folder name 1}\{random folder name 2}

(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 creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\
inprocserver32
(Default) = "\?\globalroot\Device\HarddiskVolume1\%User Temp%\{random folder name 1}\{random folder name 2}\wow.dll"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}

HKEY_CURRENT_USER\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\
inprocserver32

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}c.com
  • {BLOCKED}d5.com
  • {BLOCKED}.{BLOCKED}.221.142
  • {BLOCKED}.{BLOCKED}.59.155

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.700

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 key

[ 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\CLSID
    • {fbeb8a05-beee-4442-804e-409d6c4515e9}

Step 4

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\{random folder name 1}

Step 5

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