Philippe Vogler

Resurrecting an old AMSI Bypass

24 June 2020 ~8 min By Philippe Vogler
Amsi Bypass Powershell
While working on DoubleAgent as part of the Introduction To Red Teaming course we’re developing for RingZer0, I had a look at Anti-Malware Scan Interface (AMSI) bypasses. One of the objectives I had was to find a new way to evade AMSI. As with my DoubleAgent work, this did not lead to the identification of a novel finding, but instead revealed that old techniques can be revived with minimal work. This blog post describes how to resurrect the original DLL hijack documented by Cn33liz by extending it to simply define the typically exported functions found in amsi.dll in a fake DLL. This gives a low privileged user an AMSI bypass if they can write to a directory.

Masquerading Windows processes like a DoubleAgent.

23 April 2020 ~13 min By Philippe Vogler
Anti-Virus Malware Persistence Post-Exploitation Sysmon Windows
I’ve been spending some time building new content for our Introduction to Red Teaming course, which has been great for diving into AV/EDR bypass techniques again. In this blog post, I will demonstrate how to re-weaponise the old “DoubleAgent” technique, making endpoint security products do the hacking work for us. One known vector to shimmy past AV solutions is to use process injections. At BlackHat 2019, a number of process injection techniques were presented by Itzik Kotler. A typical code injection implementation using known WINAPI functions, such as the combination of VirtualAlloc, WriteProcessMemory and CreateRemoteThread are well known by endpoint security solutions and will often raise alerts. Whether static or dynamic analysis kicks in, the chances of remaining undetected when using these functions are close to NULL. Alas, the cat and mouse game keeps going endlessly.