DripLoader

Evasive shellcode loader for bypassing event-based injection detection (PoC)

DripLoader (PoC)

msbuild

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.

DripLoader evades common EDRs by:

  • using the most risky APIs possible like NtAllocateVirtualMemory and NtCreateThreadEx
  • 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

What does DripLoader do

  • Identifies a base address suitable for our payload
  • Reserves enough AllocationGranularity (64kB) sized, NO_ACCESS memory segments at the base address
  • Loops over those
    • Allocating PageSize (4kB) sized, writable segments
    • Writing shellcode
    • Reprotecting as RX
  • Overwrites prologue of one ntdll function in the remote process memory space with a jmp to 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.

And so

  • 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 in ntdll.

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 loader

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