Analysis by: Anthony Joe Melgarejo
 Modified by: Rhena Inocencio
ALIASES:

PHP/WebShell.NAW (ESET), PHP.RSTBackdoor (Symantec)

 PLATFORM:

Windows, Linux

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

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

  TECHNICAL DETAILS

File Size: Varies
File Type: Script
Initial Samples Received Date: 09 Feb 2016

Arrival Details

This malware arrives via the following means:

  • May be uploaded and installed on a web server by a remote malicious user after gaining access to the server.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Manipulate files and directories (download, execute, create, change permissions)
  • List running processes
  • Perform UDP DDOS
  • Execute SQL commands
  • Perl and PHP back connect
  • Generate hashes
  • Remove shell
  • Deface the site and report to Zone-H

NOTES:

Once this PHP script is installed, the remote user may then launch a backdoor on the affected system. Opening the page, the malicious user is shown the following user interface:

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.330.01
FIRST VSAPI PATTERN DATE: 09 Feb 2016
VSAPI OPR PATTERN File: 12.331.00
VSAPI OPR PATTERN Date: 10 Feb 2016

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_MADSHELL.A. 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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