Kernel Thread Stack Walking: How Anti-Cheats Trace Execution to Unbacked RAM

The Challenge of Memory-Only Cheat Execution

When game cheats inject code into memory (using manual mapping or reflective DLL injection), they avoid creating files on disk. To detect these stealthy memory execution patterns, modern kernel anti-cheat engines (Riot Vanguard, Easy Anti-Cheat, BattlEye) utilize Thread Stack Walking.

How Stack Walking Functions in the Windows Kernel

Whenever a function executes in Windows, CPU registers push the caller return address onto the execution stack:

1. Stack Frame Traversal: Anti-cheat routines call internal kernel APIs (e.g., RtlWalkFrameChain or custom unwind metadata parsers) to inspect every return pointer currently residing on the thread stack.
2. Virtual Memory Allocation Check (VAD Walk): For every return address on the stack, the anti-cheat queries the process Virtual Address Descriptor (VAD) tree to determine if that memory region is backed by a legitimate signed .dll file on disk.
3. The Unbacked Memory Trap: If a return address points to memory allocated with PAGE_EXECUTE_READWRITE with no corresponding disk file (unbacked memory), the anti-cheat flags an immediate code injection violation.

Synthetic Stack Spoofing & Why It Fails

Advanced cheat authors attempt "Stack Spoofing" by overwriting return addresses with pointers to legitimate Windows DLLs (like ntdll.dll). However, modern anti-cheats validate the entire unwind chain against x64 exception handling metadata (.pdata), flagging corrupted unwind chains instantly.

Review our analysis on BattlEye MmUnloadedDrivers scanning and kernel forensics.

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