An educational project analyzing Valve Anti-Cheat (VAC) as it operated in CS:GO - how it worked, how it was bypassed, and why the industry moved to kernel-level anti-cheat. Based on the reverse engineering work by Daniel Krupinski.
Disclaimer: This project is strictly educational.
Note: The original bypass (and the Rust reimplementation in this repo) was coded for 32-bit Steam. Current Steam is 64-bit, so this project likely does not work anymore unless it is upgraded to 64-bit.
How VAC works internally - module architecture, detection mechanisms (IAT hook detection, VMT validation, handle enumeration, driver scanning), encryption protocols (ICE cipher, XOR, MD5, CRC32), and the inherent limitations of user-mode anti-cheat against kernel-level threats.
How ~200 lines of C completely disable VAC - the page size vulnerability, IAT hook chain, GetProcAddress interception, failsafe mechanisms, and defensive takeaways explaining why modern anti-cheat moved to Ring 0.
Rust reimplementation of the original bypass (32-bit only): vac-bypass-rs/ with entrypoint vac-bypass-rs/src/lib.rs. Build and test instructions in vac-bypass-rs/README.md.
Other user-mode bypass strategies (syscall poisoning, file mapping manipulation, report layer poisoning, etc.), whether VAC's encrypted comms can be intercepted, and threats VAC cannot address (DMA, network cheats, kernel drivers, BYOVD).
How Daniel likely reverse engineered the VAC modules from compiled 32-bit DLLs into readable C source - module capture techniques, defeating XOR string obfuscation, reconstructing the API resolution layer, function-by-function disassembly using byte-pattern signatures, mapping data structures from buffer offsets, reversing the ICE cipher, and what properties of VAC made it a feasible target.
- Daniel Krupinski: reverse engineering and original implementations
- VAC: reconstructed VAC module source code
- VAC-Bypass: VAC bypass implementation
- License: MIT