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Backdoor.Win32.BADIIS.A

July 04, 2023
 Analysis by: Melvin Jhun Palbusa
 ALIASES:

Win32:BackdoorX-gen [Trj] (AVAST)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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.

  TECHNICAL DETAILS

File Size:

291,328 bytes

File Type:

DLL

Memory Resident:

No

Initial Samples Received Date:

30 Jun 2023

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.

Other Details

This Backdoor does the following:

  • It modifies responses to HTTP requests from selected search engine web crawlers to serve a malicious JavaScript file, potentially redirect code that would force the search engine to follow the redirect and index the content of the attacker’s choice
    • It requires the following parameters of the handled requests:
      • Content-Type header is set to text/html
      • The relative URL of the request contains one of the following substrings:
        • index.php
      • User-Agent header contains one of the following substrings:
        • baidu
        • sogou
        • yisou
        • baidu.com
        • sogou.com
        • so.com
        • sm.cn
  • It replaces responses to HTTP requests from web crawlers with attacker-controlled content.
    • Search engine crawler requests are recognized when the following two conditions matched:
      • The request URL contains one of these substrings:
        • .php
        • .asp
        • .aspx
        • .jsp
        • .html
        • .htm
      • The User-Agent header contains one of these substrings:
        • baidu.com
        • sogou.com
        • so.com
        • sm.cn
        • bing.com
        • google
        • coccoc
  • It replaces responses to HTTP requests from selected visitors with malicious/unwanted content.

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

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.540.05

FIRST VSAPI PATTERN DATE:

30 Jun 2023

VSAPI OPR PATTERN File:

18.541.00

VSAPI OPR PATTERN Date:

01 Jul 2023

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

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Win32.BADIIS.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:


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