Analysis by: Michael Jay Villanueva
ALIASES:

PHP/Agent.a (McAfee); PHP/Agent.GC (ESET-NOD32)

 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. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 44,661 bytes
File Type: Other
Memory Resident: No
Initial Samples Received Date: 13 Mar 2017
Payload: Connects to URLs/IPs

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

However, as of this writing, the said sites are inaccessible.

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 sends the following information:

  • HTTP_USER_AGENT - user agent
  • HTTP_REFERER - address of the page which referred the user agent to the current page
  • REMOTE_ADDR - ip address from which the user is viewing the current page
  • HTTP_HOST - contents of the host
  • PHP_SELF - filename of the currently executing script, relative to the document root

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: 9.850
FIRST VSAPI PATTERN FILE: 13.274.05
FIRST VSAPI PATTERN DATE: 13 Mar 2017
VSAPI OPR PATTERN File: 13.275.00
VSAPI OPR PATTERN Date: 14 Mar 2017

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 clean files detected as PHP_WEBSHELL.AGNY. 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.

Step 3

Scan your computer with your Trend Micro product to delete files detected as PHP_WEBSHELL.AGNY. 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.


Did this description help? Tell us how we did.