NtQueryInformationProcess Anti-Debugging

This function retrieves information about a running process. Malware are able to detect if the process is currently being attached to a debugger using the ProcessDebugPort (0x7) information class.

A nonzero value returned by the call indicates that the process is being debugged.

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.

IsDebugged Flag Anti-Debugging

While a process is running, the location of the PEB can be referenced by the location fs:[30h]. For anti-debugging, malware will use that location to check the BeingDebugged flag, which indicates whether the specified process is being debugged.

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 …

Detecting Running Process: EnumProcess API Sandbox Evasion Anti-Debugging Anti-Monitoring

Anti-monitoring is a technique used by malware to prevent security professionals from detecting and analyzing it. One way that malware can accomplish this is by using the EnumProcess function to search for specific processes, such as ollydbg.exe or wireshark.exe, which are commonly used by security professionals to monitor and analyze running processes on a system.

By detecting these processes …

Bad String Format Anti-Debugging

Bad string format is a technique used by malware to evade detection and analysis by OllyDbg, a popular debugger used by security researchers and analysts. This technique involves using malformed strings that exploit a known bug in OllyDbg, causing the debugger to crash or behave unexpectedly.

For example, the malware may use a string with multiple %s inputs, which …

INT3 Instruction Scanning Anti-Debugging

Instruction INT3 is an interruption which is used as Software breakpoints. These breakpoints are set by modifying the code at the target address, replacing it with a byte value 0xCC (INT3 / Breakpoint Interrupt).

The exception EXCEPTION_BREAKPOINT (0x80000003) is generated, and an exception handler will be raised. Malware identify software breakpoints by scanning for the byte 0xCC in the …

API Obfuscation Anti-Disassembly

API obfuscation is a technique used by malware to make it more difficult for security analysts to understand and analyze the code. This is typically done by using a technique called API hashing, which replaces the names of API functions with a hashed value. When an analyst runs the malware through a disassembler tool, the hashed values are printed instead …

Control Flow Graph Flattening Anti-Disassembly

Control flow flattening is a technique used to obfuscate the control flow of a program, in order to make it more difficult for a disassembler to accurately interpret the program's behavior. This technique involves breaking up the nesting of loops and if-statements in a program, and then hiding each of them in a case of a large switch statement. This …

Spaghetti, Junk Code Anti-Disassembly

Junk code is a technique used to add meaningless or irrelevant instructions to a program, in order to make it more difficult for a disassembler to accurately interpret the program's behavior. This technique is often used by malware authors to make it more difficult for analysts to reverse engineer the malware and understand its behavior.

Junk code can be …

Search Evasion Techniques

Search Result