POSTDump – Evading Detection And Safely Dumping LSASS Memory

Another tool to perform minidump of LSASS process using few technics to avoid detection.

POSTDump is the C# / .NET implementation of the ReactOS minidump function (like nanodump), thus avoiding call to the Windows API MiniDumpWriteDump function.

The dump logic code is saved under the POSTMinidump project, feel free to use it for your own projects. Such as NanoDump, you can encrypt or use an invalid signature for the minidump.

Usage of ProcExp driver is supported to dump/kill protected processes.

Usage

Dump LSASS:

c:\Temp>PostDump.exe --help

-o, --output        Output filename [default: Machine_datetime.dmp] (fullpath handled)

-e, --encrypt       Encrypt dump in-memory

-s, --signature     Generate invalid Minidump signature

--snap              Use snapshot technic

--fork              Use fork technic [default]

--elevate-handle    Open a handle to LSASS with low privileges and duplicate it to gain higher privileges

--duplicate-elevate Look for existing lsass handle to duplicate and elevate

--asr               Attempt LSASS dump using ASR bypass (win10/11/2019) (no signature/no encrypt)

--driver            Use Process Explorer driver to open lsass handle (bypass PPL) and dump lsass

--kill [processID]  Use Process Explorer driver to kill process and exit

--help              Display this help screen.

--version           Display version information.

Evasion

• Usage of indirect syscall along with halo’s gate technic to retrieve syscalls IDs
• No memory Allocation/Protection call is performed for indirect syscall, instead, free RWX codecave found in the current process are used
• ETW patching
• No call to MiniDumpWriteDump

Improvements Idea

• Implement more dump technics (seclogon, PPLMedic, Shtinkering ..)
• More evasion technics (callstack spoofing)
• Implement Godfault to avoid driver usage

Compilation

• You can build using .NET Framework 4.5.1 as-is.
• Depending of the CLR version installed on the system where you execute PostDump, you may need to downgrade to .NET 3.5 more info here