There are many antivirus programs available, and it can be difficult to choose the best one. $49.99 per device per year (for up to 9 devices)Ģ4/7 chat, phone and email support, AI software and tamper/uninstall prevention Once the PowerShell script finishes rebuilding the controller, it utilizes Windows Application Programming Interfaces (APIs) to load and execute the controller in memory.Free Pro is $26.99 for the first year (one device)įirewall, email security and ransomware protectionįree $50.28 per year for up to 5 devicesįree $129.49 per year for up to five devices The PowerShell script contains multiple layers of obfuscation which, when executed, decodes its contents, and rebuilds the controller. The Obfuscation – PowerShell Loader Script Sc.exe create aswSP_ArPot2 binPath= C:\windows\temp\aswArPot.sys type= kernelĬ:\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe -windowstyle hidden -executionpolicy bypass -file c:\windows\temp\SAMPLE.ps1 A short timeout is included to ensure the service is fully started, prior to the execution of the PowerShell script used to unpack and execute the controller.
AVAST RANSOMWHERE DRIVER
The threat actor executes the batch script to create and start a new service that utilizes a legitimate Avast Anti Rootkit kernel driver named aswArPot.sys. The first stage of the hijack starts with the threat actor dropping three files, a batch script, a PowerShell script, and an Avast driver, within the target system’s “C:\Windows” and “C:\Windows\Temp” directories. This article delves into the implementation of the third variant of the attack where the attacker uses a batch script as described in the third bullet point above.
AVAST RANSOMWHERE INSTALL
Additional tools are used to install and load the Avast driver in the infected system. Within this blog, we refer to this executable as the controller.
An executable that unpacks and loads in memory a small executable to control the driver.A self-contained PowerShell script, dropped alongside the Avast driver, that installs and loads the driver and executes a small number of functions to control the driver.They are listed below in the order of implementation complexity:
AVAST RANSOMWHERE DRIVERS
While the use of kernel drivers to target and kill AV and EDR solutions 1 prior to encryption has been known and discussed for some time, the abuse of a signed and valid driver from an Antivirus vendor 2 was surprisingly effective and ironic.Īt the time of writing this article, there are three different versions of the same attack. Here, as part of the Cuba’s toolset, the threat actor group executed a script that abused a function in an Avast ® Anti Rootkit kernel driver to terminate popular AV and EDR processes. We discovered novel indicators of compromise (IOCs) utilizing an interesting technique. In December 2021, Stroz Friedberg’s Incident Response Services team engaged in a Digital Forensics and Incident Response (DFIR) investigation and environment-wide recovery of a Cuba ransomware incident.
As we head into 2022, ransomware groups continue to plague our digital environment with new and interesting techniques to bypass Antivirus (AV) and Endpoint Detection and Response (EDR) solutions and ensuring the successful execution of their ransomware payloads.
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