BKDR_GRAVITYRAT.D

 Analysis by: Noel Anthony Llimos

 ALIASES:

Backdoor.MSIL.Agent.zmw (Kaspersky), Troj/MSIL-LGU (Sophos_Lite), Trojan.GenericKD.30662211 (Bitdefender)

 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:

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 connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size:

660,480 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

27 Apr 2018

Payload:

Connects to URLs/IPs, Encrypts files, , Drops files, 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 creates the following folders:

  • %AppDataLocal%\LSASS
  • %AppDataLocal%\LSASS\1.exe_Url_{Random Characters}
  • %AppDataLocal%\LSASS\Information
  • %AppDataLocal%\LSASS\Storage

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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

  • LSASS

Autostart Technique

This Backdoor drops the following files:

  • %AppDataLocal%\LSASS\1.exe_Url_5{Random Characters}\1.9.1201.10\userconfig.xml

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Backdoor Routine

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

  • http://{BLOCKED}.{BLOCKED}pdates.com:46769/GX/GX-Server.php
  • http://{BLOCKED}.{BLOCKED}pdates.com:46769/GX/GX-Server.php
  • http://{BLOCKED}.{BLOCKED}pdates.com:46769/GX/GX-Server.php
  • http://{BLOCKED}.{BLOCKED}pdates.eu:46769/GX/GX-Server.php
  • http://{BLOCKED}.{BLOCKED}pdates.eu:46769/GX/GX-Server.php
  • http://{BLOCKED}.{BLOCKED}pdates.eu:46769/GX/GX-Server.php

Information Theft

This Backdoor gathers the following data:

  • It gathers the following user account information of the affected system:
    • Account Type
    • Caption
    • Description
    • Disabled
    • Domain
    • Full Name
    • Local Account
    • Lockout
    • Name
    • Password Changes
    • Password Expiration
    • Password
    • SID
    • SID Type
    • Status
  • Open Ports on the Victim Host
  • List of all Running Processes
  • List of all available services on the system
  • MAC Address
  • OS Version
  • Computer Name
  • IP Address
  • Fingerprint - Generated MD5 hash using the information gathered in the affected system
  • Files with the following extensions in fix and removable drives:
    • .docx
    • .doc
    • .pptx
    • .ppt
    • .xlsx
    • .xls
    • .rtf
    • .pdf
  • Processor ID
  • Processor Name
  • Manufacturer of Processor
  • CPU Temperature

Other Details

This Backdoor does the following:

  • It is capable of file encryption
    • Encryption Key: "lolomycin2017"
  • It uses several Anti Virtualization techniques:
    • Searches for any additional tools used by the Hypervisor (a program installed on Virtual Machine) if it is installed on the system by checking a registry key:
      • SOFTWARE\Microsoft\Virtual Machine\Guest\Parameters
    • It creates a WMI query to the Win32_BIOS entry. If the response contains the following, the malware is considered to be in a Virtual Machine
      • VMware
      • Virtual
      • XEN
      • Xen
      • A M I
    • This malware creates a query to the Win32_Computer entry in WMI. It checks if the manufacturer has the following response to be considered running in a Virtual Machine:
      • VIRTUAL
      • VMWARE
      • VirtualBox
    • It checks if it uses a processor id of Virtual Machine
    • Performs a search for the value of the Cpu TEMP, if the response is "Not supported", it means that it runs on a Virtual Machine.
    • Searches for the following MAC Addresses that is used by a Virtual Machine:
      • 00:50:56 / VMware, Inc.
      • 00:0C:29 / VMware, Inc.
      • 00:05:69 / VMware, Inc.
      • 08:00:27 / PCS Systemtechnik GmbH (VirtualBox)
      • 00:1C:42 / Parallels, Inc
    • Checks on how many cores does the system have. If one, it is flagged as being run on a Virtual Machine

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.228.04

FIRST VSAPI PATTERN DATE:

27 Apr 2018

VSAPI OPR PATTERN File:

14.229.00

VSAPI OPR PATTERN Date:

28 Apr 2018

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

Identify and terminate files detected as BKDR_GRAVITYRAT.D

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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.
  • %AppDataLocal%\LSASS\1.exe_Url_5{Random Characters}\1.9.1201.10\userconfig.xml

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.  
  • %AppDataLocal%\LSASS
  • %AppDataLocal%\LSASS\1.exe_Url_{Random Characters}
  • %AppDataLocal%\LSASS\Information
  • %AppDataLocal%\LSASS\Storage

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_GRAVITYRAT.D. 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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