BKDR_STONEDRILL.A

 Analysis by: Cris Nowell Pantanilla

 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. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size:

227,840 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Mar 2017

Payload:

Drops files, Deletes files, Connects to URLs/IPs, Collects system information, Downloads files

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 copies of itself into the affected system:

  • %User Temp%\bd891.tmp
  • %ProgramData%\Chrome\{random filename}.exe
  • %ProgramData%\InternetExplorer\{random filename}Stp.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.. %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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 drops the following files:

  • %ProgramData%\Chrome\FileInfo.txt
  • %ProgramData%\InternetExplorer\FileInfoStp.txt
  • %User Temp%\C-Dlt-C-Trsh-T.tmp
  • %User Temp%\C-PDC-C-Cpy-T.vbs ← used to copy itself
  • %User Temp%\C-PDI-C-Cpy-T.vbs ← used to copy itself
  • %User Temp%\C-Dlt-C-Org-T.vbs ← used to delete initial copy
  • %User Temp%\C-Strt-C-Up-T.vbs ← used to create autorun registry

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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 injects codes into the following process(es):

  • User's default browser (except LaunchWinApp.exe)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name} = "%ProgramData%\InternetExplorer\{random file name}Stp.exe"

Backdoor Routine

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

  • Uninstall self
  • Get system information (OS version, Architecture, Build, Environment)
  • Get system time
  • Get malware version
  • Remote command shell
  • Screen capture
  • Download files
  • Upload files
  • Check antivirus installation and registries (McAfee, AVG, Avast, Bitdefender)

It connects to the following websites to send and receive information:

  • http://www.{BLOCKED}ervic.com/

Other Details

This backdoor does the following:

  • It is capable of wiping (deleting) files on the following locations:
    • All accessible physical drives by using the device path '\.\PhysicalDrive'.
    • All accessible logical drives by using device path '\.\X:'.
    • All folders except 'Windows' on all accessible drives.
    • Files named 'asdhgasdasdwqe%digits%' in the root folder of the disk.
  • It generates the "{random file name}.exe" by choosing random strings from the sets of strings as follows:
      %ProgramData%\{set 1}{set 2}{set 3}.exe
    • SET 1
      • AMD
      • Adobe
      • Application
      • Bitlocker
      • Browser
      • CDROM
      • CPU
      • Cash
      • Cisco
      • Cloud
      • Desktop
      • Display
      • DotNet
      • Ethernet
      • Fingerprint
      • Intel
      • Java
      • Location
      • Lockscreen
      • MFC
      • Map
      • Memory
      • Microsoft
      • Monitor
      • NFC
      • Office
      • Packet
      • Power
      • Query
      • RAM
      • ROM
      • Registery
      • Run-time
      • SQL
      • SunGard
      • Task
      • WMI
      • Windows
    • SET 2
      • Agent
      • Core
      • Data
      • Device
      • Engine
      • File
      • Firewall
      • Gaming
      • Graphic
      • Hardware
      • History
      • Media
      • Network
      • Performance
      • Server
      • Service
      • Software
      • Storage
      • System
      • VM
      • Wizard
      • boot
    • SET 3
      • API
      • APP
      • Adapter
      • Arranger
      • Backup
      • CleanUp
      • Client
      • Controller
      • Details
      • Diagnostics
      • Encryption
      • Events
      • Execute
      • Extention
      • Framework
      • Help
      • Host
      • LogOn
      • Luncher
      • Manager
      • Menu
      • Model
      • Plug
      • Policy
      • Provider
      • Proxy
      • Recovery
      • Stub
      • Tester
      • Transfer

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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.)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.266.05

FIRST VSAPI PATTERN DATE:

09 Mar 2017

VSAPI OPR PATTERN File:

13.267.00

VSAPI OPR PATTERN Date:

10 Mar 2017

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name} = "%ProgramData%\InternetExplorer{random file name}Stp.exe"

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.
%ProgramData%\Chrome\FileInfo.txt
%ProgramData%\InternetExplorer\FileInfoStp.txt
%User Temp%\C-Dlt-C-Trsh-T.tmp
%User Temp%\C-PDC-C-Cpy-T.vbs
%User Temp%\C-PDI-C-Cpy-T.vbs
%User Temp%\C-Dlt-C-Org-T.vbs
%User Temp%\C-Strt-C-Up-T.vbs

Step 5

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