Analysis by: Rika Joi Gregorio
ALIASES:

TrojanDownloader:Win32/Kuluoz.B(Microsoft), Trojan.Fakeavlock(Norton), Trojan-Downloader.Win32.Kuluoz(Ikarus), Win32/TrojanDownloader.Zortob.B trojan(Eset)

 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: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 53,248 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 03 Dec 2012

Arrival Details

This backdoor 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 backdoor drops the following copies of itself into the affected system:

  • %Application Data%\{random}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It leaves the following text files:

  • {Malware Path and Filename}.txt

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.66.217:8080/{generated value}
  • http://{BLOCKED}.{BLOCKED}.112.7:8080/{generated value}
  • http://{BLOCKED}.{BLOCKED}.131.132:8080/{generated value}
  • http://{BLOCKED}.{BLOCKED}.189.234:8080/{generated value}
  • http://{BLOCKED}.{BLOCKED}.241.208:8080/{generated value}
  • http://{BLOCKED}.{BLOCKED}.204.228:8080/{generated value}

It deletes itself after execution.

NOTES:
Upon execution, it opens the non-malicious .TXT file {Malware Path and Filename}.txt it drops in order to hide its malicious routines from the user.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.950.02
FIRST VSAPI PATTERN DATE: 30 May 2013
VSAPI OPR PATTERN File: 9.951.00
VSAPI OPR PATTERN Date: 31 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

Search and delete this file

[ 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.
  • {Malware Path and Filename}.txt

Step 4

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