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Rootkit.Win32.FETNILTER.A

June 29, 2021
 Analysis by: Paul Steven Nadera
 ALIASES:

Trojan:Win32/Retliften.A (Microsoft);

 PLATFORM:

Windows

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

  • Threat Type: Rootkit

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


This Rootkit arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It connects to a website to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

39,312 bytes

File Type:

SYS

Memory Resident:

Yes

Initial Samples Received Date:

28 Jun 2021

Payload:

Connects to URLs/IPs

Arrival Details

This Rootkit arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Other System Modifications

This Rootkit adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
SystemCertificates\ROOT\Certificates\
FEF8C731E0E7B3D13E221C7595BE3EA270B58863
Blob = {certificate data blob}

Backdoor Routine

This Rootkit connects to the following websites to send and receive information:

  • http://{BLOCKED}.{BLOCKED}.4.180:2080/u
    • Query configuration information
  • http://{BLOCKED}.{BLOCKED}.4.180:2080/p
    • Request for proxy settings to be written in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\AutoConfigURL
  • http://{BLOCKED}.{BLOCKED}.4.180:2080/s
    • Query list of target IP addresses that will redirect to {BLOCKED}.{BLOCKED}.10.244:{BLOCKED}
    • http://{BLOCKED}.{BLOCKED}.4.180:2080/h?
      • Ping C2
    • http://{BLOCKED}.{BLOCKED}.4.180:2080/c
      • Query root certificate to be written in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SystemCertificates\ROOT\Certificates\
    • http://{BLOCKED}.{BLOCKED}.4.180:2080/v?v={Version Number}&m={Hash}
      • Updates itself to latest version

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

    Other Details

    This Rootkit adds the following registry keys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
    SystemCertificates\ROOT\Certificates\
    {Certificate Name from C2 Server}

    It does the following:

    • It must be registered kernel driver service to continue with its malicious routine.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.808.08

FIRST VSAPI PATTERN DATE:

28 Jun 2021

VSAPI OPR PATTERN File:

16.809.00

VSAPI OPR PATTERN Date:

29 Jun 2021

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

Restart in Safe Mode

[ Learn More ]

Step 4

Disable this malware service

[ Learn More ]
  •  netfilter

Step 5

Delete this registry value

[ 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\SOFTWARE\Microsoft\SystemCertificates\ROOT\Certificates\FEF8C731E0E7B3D13E221C7595BE3EA270B58863
    • Blob = {certificate data blob}

Step 6

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\SOFTWARE\Microsoft\SystemCertificates\ROOT\Certificates\FEF8C731E0E7B3D13E221C7595BE3EA270B58863
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\netfilter

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Rootkit.Win32.FETNILTER.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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