Evasive shellcode loader for bypassing event-based injection detection, without necessarily suppressing event collection (still added direct syscalls, just so I don't have to deal with AV). The project is aiming to highlight limitations of event-driven injection identification, and show the need for more advanced memory scanning and smarter local agent software inventories in EDR.
- using the most risky APIs possible like
NtAllocateVirtualMemoryandNtCreateThreadEx - blending in with call arguments to create events that vendors are forced to drop or log&ignore due to volume
- avoiding multi-event correlation by introducing delays
- Identifies a base address suitable for our payload
- Reserves enough
AllocationGranularity(64kB) sized,NO_ACCESSmemory segments at the base address - Loops over those
- Allocating
PageSize(4kB) sized, writable segments - Writing shellcode
- Reprotecting as
RX
- Allocating
- Overwrites prologue of one
ntdllfunction in the remote process memory space with ajmpto our base - Drops a thread on that trampoline
I'll explain the thinking behind each step in a blog post coming end of the week.
- It's able to fully bypass many EDR injection detections, including Defender ATP.
- Bypasses simple thread-centric scanners like
Get-InjectedThread. Persisting within a process is another story, and this is up to the payload author. - It is
sRDI-compatible, but if your payload creates another local thread you will lose the benefit of thread start address inntdll.
To test it out of the box
- compile/download
- XOR your binary shellcode blob file with default key 0x08, name it
blob.bin - place both files in the same directory
- run it and follow the prompts or ./DripLoader.exe <target_pid> <delay_per_step_ms>
I attached an example MessageBox blob for your pleasure, be aware though it's size is unrealistically small for a payload.
ASCII arts are essential for tools like this to work
