With Veil’s 2.0 release, several powershell payloads were released which we wanted to detail a bit more here.
powershell/VirtualAlloc uses the VirtualAlloc() pattern to inject shellcode into memory. The concept was adapted from Matthew Graeber’s excellent article concerning powershell shellcode injection. The powershell string is then compressed and a .bat launcher is built, which will invoke the powershell binary with a command that decompresses and runs the original powershell file. The .bat launcher does basic x86/x64 architecture detection to attempt to work on multiple platforms.
powershell/DownloadVirtualAlloc takes adapts the technique from ObscureSecurity’s writeup to download a secondary powershell payload from a separate sever, which it then runs. A small encrypted command is output which will download a larger secondary powershell stage from a specified webserver and launch it in memory.
powershell/PsexecVirtualAlloc is similar to the VirtualAlloc module, but it builds a metasploit .rc resource file that’s compatible with metasploit’s psexec_command module. When you run the produced resource file in metasploit, the psexec_command module is selected and the COMMAND parameter is properly set to the powershell VirtualAlloc launcher. You can then set the RHOSTS, SMBUser and SMBPass and then psexec away, utilizing pure powershell for AV-evading goodness.
Also of note, Veil now has a development branch on its GitHub page. New bug fixes and features will be pushed here first, but with no guarantees to stability. If you have any questions, or if something breaks, please get in touch with us in #veil on freenode!