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Backdoor.Win32.FLAWEDGRACE.AB

March 05, 2019
 Analysis by: Arvin Roi Macaraeg
 ALIASES:

Trojan.Win32.Yakes.yltz(KASPERSKY), Backdoor:Win32/GraceWire.D!dha(MICROSOFT)

 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:

Dropped by other malware, Downloaded from the Internet


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:

683,944 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Feb 2019

Payload:

Connects to URLs/IPs, 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 drops the following files:

  • %All Users Profile%\{System Volume Hash}.dat -> run with admin privileges
  • %All Users Profile%\{System Volume Hash}.bin -> run with admin privileges
  • %ProgramData%\{System Volume Hash}.bin -> run without admin privileges
  • %ProgramData%\{System Volume Hash}.dat -> run without admin privileges

(Note: %All Users Profile% is the common user's profile folder, which is usually C:\Documents and Settings\All Users on Windows 2000, XP, and Server 2003, or C:\ProgramData on Windows Vista, 7, and 8. . %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData in Windows Vista, 7, and 8.)

It adds the following processes:

  • cmd /C net localgroup

Other System Modifications

This Backdoor adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
SoftwareSASGeneration = "1"

Backdoor Routine

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

  • Downloads File (target_download)
  • Load and Unload Modules (target_module_load, target_module_load_external, target_module_unload)
  • Get Passwords (target_passwords)
  • RDP Session (target_rdp)
  • Reboot system (target_reboot)
  • Delete Files (target_remove)
  • Run Scripts (target_script)
  • List of Servers (target_servers)
  • Update Version (target_update)
  • Upload File (target_upload)
  • Gather system information (desktop_stat)
  • Force shutdown (destroy_os)

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}.{BLOCKED}.16.61:443

Information Theft

This Backdoor gathers the following data:

  • Computer Name
  • User's Credentials (password)
  • OS Version
  • Architecture
  • Domain Name
  • Username
  • Admin priveleges (User Account Control)
  • Boot
  • Locale
  • Antivirus Product Name obtained via WMI query
  • Malware installed time
  • Malware version
  • Local IP

Other Details

This Backdoor does the following:

  • This Backdoor accepts the following parameters:
    • -i (process ID)
    • -sn (service name)
    • -p (pipe)
    • -m (module)
  • This Backdoor find IP address using the following process:
    • cmd /C ipconfig | findstr /R /%System Root%"IPv4 Address"

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.840.04

FIRST VSAPI PATTERN DATE:

27 Feb 2019

VSAPI OPR PATTERN File:

14.841.00

VSAPI OPR PATTERN Date:

28 Feb 2019

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 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

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\Windows\CurrentVersion\Policies\System
    • SoftwareSASGeneration = "1"

Step 5

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.
  • %All Users Profile%\{System Volume Hash}.dat
  • %All Users Profile%\{System Volume Hash}.bin
  • %ProgramData%\{System Volume Hash}.bin
  • %ProgramData%\{System Volume Hash}.dat

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.FLAWEDGRACE.AB. 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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