Analysis by: Maureen Reyes
 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: Propagates via email, 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.

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

  TECHNICAL DETAILS

File Size: 285,691 bytes
File Type: BIN
Memory Resident: Yes
Initial Samples Received Date: 17 Jul 2018
Payload: Connects to URLs/IPs, Adds service

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:

  • RasPbFile

Autostart Technique

This Backdoor adds and runs the following services:

    • Service Name: gpsvcs
    • Description: The service is responsible efor applying settings configured by administrators for the computer and users through the Group Policy component.
    • Display Name: Group Policy Service
    • Image Path: "{Malware Path and Filename} 3"

Other Details

This Backdoor does the following:

  • It connects to the following URL:
    stonefamily.{BLOCKED}onefamily.ml
  • It requires a specific Machine GUID to decrypt its malicious code
  • It requires the following files to run properly:
    • {Malware Path}\webfilter.dll
    • {Malware Path}\Dislite.exe
  • It injects to %System%\msiexec.exe multiple times using two arguments {2 or 3} to specify which part of the malicious code will be loaded into the memory of the executable

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

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.412.08
FIRST VSAPI PATTERN DATE: 30 Jul 2018
VSAPI OPR PATTERN File: 14.413.00
VSAPI OPR PATTERN Date: 31 Jul 2018

Step 1

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 2

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

Step 3

Restart in Safe Mode, and then delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services
    • gpsvcs

Step 4

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_TGNDIS.ZYFG-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.

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_TGNDIS.ZYFG-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:


Did this description help? Tell us how we did.