Analysis by: Raighen Sanchez
 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • 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 does not have any propagation routine.

  TECHNICAL DETAILS

File Size: 363,520 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 06 Jan 2025
Payload: Connects to URLs/IPs, Collects system information, Steals information

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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • cab0a9b41f6e44c24b9fd412b5e538c0

Propagation

This Backdoor does not have any propagation routine.

Rootkit Capabilities

This Backdoor does not have rootkit capabilities.

Information Theft

This Backdoor gathers the following data:

  • Hostname
  • Username
  • Locale

Other Details

This Backdoor connects to the following URL(s) to check for an Internet connection:

  • https://www.bing.com

It does the following:

  • It impersonates the logged on user.
  • It uses the following URL to use Slack's API for its malicious purposes:
    • https://{BLOCKED}k.com/api/chat.postMessage
    • https://{BLOCKED}k.com/api/chat.update
    • https://{BLOCKED}k.com/api/chat.delete
    • https://{BLOCKED}k.com/api/files.upload?&channels=
    • https://{BLOCKED}k.com/api/conversations.list?exclude_archived=true
    • https://{BLOCKED}k.com/api/conversations.create
    • https://{BLOCKED}k.com/api/conversations.history?limit=200&channel=
  • The Slack communication was established through the use of this hardcoded authentication token:
    • {BLOCKED}26427959425-5707141283990-5726497507873-511646c6920d425fc62e147145bc56db → Inacessible; token revoked
  • It checks for the presence of the following files in order to proceed with its intended routine:
    • list.txt → encrypted payload
    • output.txt → encrypted payload

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.822.03
FIRST VSAPI PATTERN DATE: 06 Jan 2025
VSAPI OPR PATTERN File: 19.823.00
VSAPI OPR PATTERN Date: 07 Jan 2025

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.Win64.LEGIRAT.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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