NtQueryObject Anti-Debugging

This function retrieves object information. By calling this function with the class ObjectTypeInformation will retrieve the specific object type (debug) to detect the debugger.

OutputDebugString Anti-Debugging

This Windows API is often used by developers for debugging purpose. It will display a text to the attached debugger. This API is also used by Malware to open a communication channel between one or multiple processes.

It is possible to use OutputDebugString in addition of GetLastError / SetLastError to detect debugger presence.

EventPairHandles Anti-Debugging

An EventPair Object is an event constructed by two _KEVENT structures which are conventionally named High and Low.

There is a relation between generic Event Objects and Debuggers because they must create a custom event called DebugEvent able to handle exceptions. Due to the presence of events owned by the Debugger, every information relative to the events of a …

CsrGetProcessID Anti-Debugging

This function is undocumented within OpenProcess. It can be used to get the PID of CRSS.exe, which is a SYSTEM process. By default, a process has the SeDebugPrivilege privilege in their access token disabled.

However, when the process is loaded by a debugger such as OllyDbg or WinDbg, the SeDebugPrivilege privilege is enabled. If a process is able …

CloseHandle, NtClose Anti-Debugging

When a process is debugged, calling NtClose or CloseHandle with an invalid handle will generate a STATUS_INVALID_HANDLE exception.

The exception can be cached by an exception handler. If the control is passed to the exception handler, it indicates that a debugger is present.

Heap Flag Anti-Debugging

ProcessHeap is located at 0x18 in the PEB structure. This first heap contains a header with fields used to tell the kernel whether the heap was created within a debugger. The heap contains two fields which are affected by the presence of a debugger. These fields are Flags and ForceFlags.

The values of Flags and ForceFlags are normally …

NtGlobalFlag Anti-Debugging

The information that the system uses to determine how to create heap structures is stored at an undocumented location in the PEB at offset 0x68. If the value at this location is 0x70, we know that we are running in a debugger.

The NtGlobalFlag field of the Process Environment Block (0x68 offset on 32-Bit and 0xBC on …

RDTSC Anti-Debugging

The Read-Time-Stamp-Counter (RDTSC) instruction can be used by malware to determine how quicky the processor executes the program's instructions. It returns the count of the number of ticks since the last system reboot as a 64-bit value placed into EDX:EAX.

It will execute RDTSC twice and then calculate the difference between low order values and check it with …

GetLocalTime, GetSystemTime, timeGetTime, NtQueryPerformanceCounter Sandbox Evasion Anti-Debugging

When a debugger is present, and used to single-step through the code, there is a significant delay between the executions of the individual instructions, when compared to native execution.

Detecting Window with FindWindow API Anti-Debugging Anti-Monitoring

The FindWindowA / FindWindowW function can be used to search for windows by name or class.

It is also possible to use EnumWindows API in conjunction with GetWindowTextLength and GetWindowText to locate a piece of string that could reveal the presence of a known debugger.

Some Known Debuggers

ImmunityDebugger
OllyDbg
IDA
x64dbg / …

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