LockBit ransomware takes as little as five minutes to deploy the encryption routine on target systems once it lands on the victim network. LockBit attacks leave few traces for forensic analysis as the malware loads into the system memory, with logs and supporting files removed upon execution. In one case, they found that the attack began from a compromised Internet Information Server that launched a remote PowerShell script calling another script embedded in a remote Google Sheets document. This script connects to a command and control server to retrieve and install a PowerShell module for adding a backdoor and establish persistence. To evade monitoring and go unnoticed in the logs, the attacker renamed copies of PowerShell and the binary for running Microsoft HTML Applications (mshta.exe); this prompted Sophos to call this a “PS Rename“ attack. The backdoor is responsible for installing attack modules and executes a VBScript that downloads and executes a second backdoor on systems restart. An overview of the attack is available below:
The attack scripts also attempt to bypass Windows 10’s built-in anti-malware interface. Artifacts found on attacked systems suggest the use of scripts based on the PowerShell Empire post-exploitation framework. Their purpose was to collect details about the victim network, identify valuable systems, and check for available defense solutions. In three hours, the malware encrypted about 25 servers and 225 computer systems.