This research was conducted by Ross Inman (@rdi_x64) from NCC Group Cyber Incident Response Team. You can find more here Incident Response – NCC Group

Summary

tl;dr

This post explores some of the TTPs employed by a threat actor who were observed deploying LockBit 3.0 ransomware during an incident response engagement.

Below provides a summary of findings which are presented in this blog post:

• Initial access via SocGholish.
• Establishing persistence to run Cobalt Strike beacon.
• Disabling of Windows Defender and Sophos.
• Use of information gathering tools such as Bloodhound and Seatbelt.
• Lateral movement leveraging RDP and Cobalt Strike.
• Use of 7zip to collect data for exfiltration.
• Cobalt Strike use for Command and Control. 
• Exfiltration of data to Mega.
• Use of PsExec to push out ransomware.

LockBit 3.0

LockBit 3.0 aka “LockBit Black”, noted in June of this year has coincided with a large increase of victims being published to the LockBit leak site, indicating that the past few months has heralded a period of intense activity for the LockBit collective.

In the wake of the apparent implosion of previous prolific ransomware group CONTI [1], it seems that the LockBit operators are looking to fill the void; presenting a continued risk of encryption and data exfiltration to organizations around the world.

TTPs

Initial Access

Initial access into the network was gained via a download of a malware-laced zip file containing SocGholish. Once executed, the download of a Cobalt Strike beacon was initiated which was created in the folder C:ProgramDataVGAuthService with the filename VGAuthService.dll. Along with this, the Windows command-line utility rundll32.exe is copied to the folder and renamed to VGAuthService.exe and used to execute the Cobalt Strike DLL.

PowerShell commands were also executed by the SocGholish malware to gather system and domain information:

• powershell /c nltest /dclist: ; nltest /domain_trusts ; cmdkey /list ; net group 'Domain Admins' /domain ; net group 'Enterprise Admins' /domain ; net localgroup Administrators /domain ; net localgroup Administrators ;
• powershell /c Get-WmiObject win32_service -ComputerName localhost | Where-Object {$_.PathName -notmatch 'c:win'} | select Name, DisplayName, State, PathName | findstr 'Running' 

Persistence

A persistence mechanism was installed by SocGholish using the startup folder of the infected user to ensure execution at user logon. The shortcut file C:\Users\\AppData\Roaming\Microsoft\Windows\Start MenuProgramsStartupVGAuthService.lnk was created and configured to execute the following command which will run the Cobalt Strike beacon deployed to the host:

C:\ProgramData\VGAuthService\VGAuthService.exe

C:\ProgramData\VGAuthService\VGAuthService.dll,DllRegisterServer

Defence Evasion

Deployment of a batch script named 123.bat was observed on multiple hosts and was deployed via PsExec. The script possessed the capabilities to uninstall Sophos, disable Windows Defender and terminate running services where the service name contained specific strings. The contents of the batch script are provided below:

The ransomware binary used also clears key Windows event log files including Application, System and Security. It also prevents any further events from being written by targeting the EventLog service.

Discovery

Bloodhound was executed days after the initial SocGholish infection on the patient zero host. The output file was created in the C:\ProgramData directory and had the file extension .bac instead of the usual .zip, however this file was still a zip archive.  

A TGS ticket for a single account was observed on patient zero in a text file under C:\ProgramData. It is highly likely the threat actor was gathering the ticket to attempt to crack the password, associated with the account, offline.

Seatbelt [2] was also executed on the patient zero host alongside Bloodhound. Security-orientated information about the host gathered by Seatbelt was outputted to the file C:\ProgramData\seat.txt.

Lateral Movement

The following methods were utilized to move laterally throughout the victim network:

• Cobalt Strike remotely installed temporary services on targeted hosts which executed a Cobalt Strike beacon. An example command line of what the services were configured to run is provided below:
  
  rundll32.exe c:\programdata\svchost1.dll,DllRegisterServer

• RDP sessions were established using a high privileged account the threat actor had compromised prior.

Collection

7zip was deployed by the adversary to compress and stage data from folders of interest which had been browsed during RDP sessions.

Command and Control

Cobalt Strike was the primary C2 framework utilized by the threat actor to maintain their presence on the estate as well as laterally move.

Exfiltration Using MegaSync

Before deploying the ransomware to the network, the threat actor began to exfiltrate data to Mega, a cloud storage provider. This was achieved by downloading Mega sync software onto compromised hosts, allowing for direct upload of data to Mega.

Impact

The ransomware was pushed out to the endpoints using PsExec and impacted both servers and end-user devices. The ransomware executable was named zzz.exe and was located in the following folders:

• C:\Windows
• C:\ProgramData
• C:\Users\\Desktop

Recommendations

1. Ensure that both online and offline backups are taken and test the backup plan regularly to identify any weak points that could be exploited by an adversary.
2. Restrict internal RDP and SMB traffic so that only hosts that are required to communicate via these protocols are allowed to.   
3. Monitor firewalls for anomalous spikes in data leaving the network.
4. Block traffic to cloud storage services such as Mega which have no legitimate use in a corporate environment.
5. Provide regular security awareness training.

If you have been impacted by LockBit, or currently have an incident and would like support, please contact our Cyber Incident Response Team on +44 161 209 5148 or email cirt@nccgroup.com.

Indicators of Compromise

MITRE ATT CK®

1. https://www.bleepingcomputer.com/news/security/conti-ransomware-finally-shuts-down-data-leak-negotiation-sites/
2. https://github.com/GhostPack/Seatbelt

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