Analysis by: Francis Xavier Antazo
 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

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

It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 13,319 bytes
File Type: Other
Memory Resident: No
Initial Samples Received Date: 12 Oct 2015

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.

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

Backdoor Routine

This backdoor connects to the following websites to send and receive information:

  • {BLOCKED}38.com
  • {BLOCKED}e8.com
  • {BLOCKED}88.com
  • {BLOCKED}cb.com

NOTES:

This backdoor is a PHP script injected in compromised web servers.

This backdoor downloaded data from its C&C and appends the downloaded code to itself.

This Backdoor does nothing if the user agent contains any of the following strings:

  • google
  • slurp
  • msnbot
  • ia_archiver
  • yandex
  • rambler

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.976.04
FIRST VSAPI PATTERN DATE: 12 Oct 2015
VSAPI OPR PATTERN File: 11.977.00
VSAPI OPR PATTERN Date: 13 Oct 2015

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 to delete files detected as PHP_WEBSHELL.XUK. 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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