The cybercriminals behind the TrickBot malware, who are believed to be based in Russia, have been using a new PowerShell backdoor in recent attacks aimed at high-value targets, SentinelLabs revealed on Thursday.
Initially discovered in 2016, TrickBot is the successor of the Dyre Trojan. The malware has seen numerous updates and improvements since it was discovered, and it has been used in a large number of attacks, many focused on enterprise environments.
Called PowerTrick, the recently discovered backdoor is being deployed, at least in some cases, as a PowerShell task through normal TrickBot infections. The malware is simple, mainly designed to execute commands and return the results in Base64 format, SentinelLabs says.
PowerTrick has been used in attacks aimed at important targets, such as financial institutions.
The bot activities include performing an initial check-in, resetting throttle time or exit (depending on response), sit in a loop (waiting for the next commands to be executed), execute received command, send back the results or an error message, and sleep for the throttle amount.
The new offensive tool, SentinelLabs security researchers say, is being used for profiling and pivoting, and is being leveraged in conjunction with various other frameworks and offensive tools, either paid or freely available for download.
In attacks involving the PowerTrick backdoor, the cybercriminals also commonly utilize other PowerShell utilities for a variety of tasks, such as the ‘letmein.ps1’ stager for the open-source exploitation framework Metasploit.
The script is frequently used to pivot the infection to another framework, but also to detonate on other systems after pivoting.
After profiling the compromised systems and network, the threat actor starts the cleanup operation, which involves removing all files that did not execute properly, or moves laterally to high-value systems, such as financial gateways.
SentinelLabs’ researchers were able to link the PowerTrick backdoor to malware such as TrickBot Anchor DNS (which was initially detailed in October 2019) and TerraLoader with the “more_eggs” backdoor onboard, but also observed the malware being used for direct shellcode execution.
“The end-goal of the PowerTrick backdoor and its approach is to bypass restrictions and security controls to adapt to the new age of security controls and exploit the most protected and secure high-value networks,” SentinelLabs said.
Related: TrickBot Makes Heavy Use of Evasion in Recent Attacks
Related: TrickBot Tricks U.S. Users into Sharing their PIN Codes
