Debug Registers, Hardware Breakpoints

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

Featured Windows API's

Below, you will find a list of the most commonly used Windows API's that are currently utilized by malware authors for current evasion technique. This list is meant to provide an overview of the API's that are commonly used for this purpose. If there are any API's that you feel should be included on this list, please do not hesitate to contact us. We will be happy to update the list and provide any additional information or documentation that may be helpful.

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;
}

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.