➔
search
✕

Backdoor.PHP.DEFACER.A

January 10, 2022
 Analysis by: Maria Emreen Viray
 PLATFORM:

Windows, Mac, Linux

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

  TECHNICAL DETAILS

File Size:

2,108 bytes

File Type:

PHP

Memory Resident:

No

Initial Samples Received Date:

03 Jan 2022

Payload:

Executes commands

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 files:

  • {Server's document root directory}\.htaccess

Other System Modifications

This Backdoor deletes the following files:

  • {Server's document root directory}\.user.ini

Backdoor Routine

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

  • Execute arbitrary code

Other Details

This Backdoor requires being hosted on a web server in order to proceed with its intended routine.

NOTES:

This Backdoor does the following:

  • It continues with routine if it receives value through request parameter name "403"
  • It retrieves and executes the contents of the URL received through the request parameter name "php"

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

17.292.08

FIRST VSAPI PATTERN DATE:

03 Jan 2022

VSAPI OPR PATTERN File:

17.293.00

VSAPI OPR PATTERN Date:

04 Jan 2022

Step 1

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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.
  • {Server's document root directory}\.htaccess

Step 4

Scan your computer with your Trend Micro product to delete files detected as Backdoor.PHP.DEFACER.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 the following Trend Micro Support pages for more information:

Step 5

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.  

  • {Server's document root directory}\.user.ini


Did this description help? Tell us how we did.