Debug Registers, Hardware Breakpoints

Created the Friday 13 November 2020. Updated 1 year, 2 months ago.

Registers DR0 through DR3 contain the linear address associated with one of the four hardware breakpoint conditions. For anti-debugging, malware will check the contents of the first four debug registers to see if the hardware breakpoint has been set.

Technique Identifiers

U0127 B0001.005

Technique Tag

DR0

Code Snippets

#include <windows.h>
#include <stdio.h>

int main() {

    HANDLE thread = GetCurrentThread();
    CONTEXT threadContext;
    int errorCode;

    memset(&threadContext, 0, sizeof(CONTEXT));
    threadContext.ContextFlags = CONTEXT_ALL;

    if( !GetThreadContext(thread, &threadContext) ){
        errorCode = GetLastError();
        puts("Could not get thread context");
        return errorCode;
    }

    if( threadContext.Dr0 || threadContext.Dr1 || threadContext.Dr2 || threadContext.Dr3 ){
        puts("Detected");
    }
    else{
        puts("Undetected");
    }

    return 0;
}

About Author Open Snippet

Author: Lexsek / Target Platform: Windows

Detection Rules

rule:
  meta:
    name: check for hardware breakpoints
    namespace: anti-analysis/anti-debugging/debugger-detection
    author: michael.hunhoff@fireeye.com
    scope: function
    mbc:
      - Anti-Behavioral Analysis::Debugger Detection::Hardware Breakpoints [B0001.005]
    references:
      - https://github.com/LordNoteworthy/al-khaser/blob/master/al-khaser/AntiDebug/HardwareBreakpoints.cpp
    examples:
      - al-khaser_x86.exe_:0x42035D
  features:
    - and:
      - api: kernel32.GetThreadContext
      - number: 0x10010 = CONTEXT_DEBUG_REGISTERS
      - offset: 0x4 = DR0
      - offset: 0x8 = DR1
      - offset: 0xC = DR2
      - offset: 0x10 = DR3
      - count(mnemonic(cmp)): 4 or more

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.