Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This backdoor may be hosted on a website and run when a user accesses the said website.

It executes commands from a remote malicious user, effectively compromising the affected system.

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

  TECHNICAL DETAILS

File Size: 5,560 bytes
File Type: Script
Memory Resident: No
Initial Samples Received Date: 04 Nov 2011
Payload: Connects to URLs/IPs, Downloads files

Arrival Details

This backdoor may be hosted on a website and run when a user accesses the said website.

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

  • TCP 6667

It connects to any of the following IRC server(s):

  • {BLOCKED}c.{BLOCKED}irc.org

It joins any of the following IRC channel(s):

  • #Gurit
  • #laknat

It executes the following commands from a remote malicious user:

  • Logout connection
  • Send emails
  • Download files
  • Switch server
  • Launch UDP and TCP flooding method
  • Switch server

Download Routine

This backdoor connects to the following URL(s) to download its configuration file:

  • http://{BLOCKED}co.kr/r57.txt

It connects to the following URL(s) to download its component file(s):

  • http://{BLOCKED}co.kr/a.jpg
  • http://{BLOCKED}co.kr/pitbull.jpg

It saves the files it downloads using the following names:

  • /tmp/msdp - detected as BKDR_PERLBOT.SMO
  • /tmp/marsudi - detected as BKDR_PERLBOT.SMO

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

NOTES:

It sets the permission of the downloaded file to:

  • Full
  • Read and Execute

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.546.02
FIRST VSAPI PATTERN DATE: 04 Nov 2011

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 PHP_IRCBOT.AHC

    • BKDR_PERLBOT.SMO

Step 3

Close all opened browser windows

Step 4

Scan your computer with your Trend Micro product to delete files detected as PHP_IRCBOT.AHC . 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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