VaultSec Lab

In the ever-evolving landscape of AV/EDR (Antivirus/Endpoint Detection and Response) defense mechanisms, traditional syscall execution has become increasingly vulnerable to detection. These tools utilize user-mode hooks and instrumentation callbacks to flag anomalous behavior, such as syscalls that don't return to ntdll.dll. This blog delves into how to create evasive shellcode loader in GO, fetching and decrypting AES-encrypted shellcode from a server and executing it stealthily using indirect syscalls.

VEH can be useful in security research and bypassing certain security mechanisms, including antiviruses or EDR systems, as it allows custom handlers to be implemented at a low level.

Bitdefender GravityZone is known for its effective EDR capabilities, leveraging user-mode API hooks to detect and mitigate suspicious behaviors. However, like many EDRs, it relies heavily on hooking functions within libraries such as ntdll.dll. By understanding its methodology, we can explore a technique, which bypasses these hooks entirely.