Evasion using direct Syscalls Antivirus/EDR Evasion

In the Windows operating system, conventional malware frequently utilizes strategies involving the invocation of specific functions from the kernel32.dll library, such as VirtualAlloc, VirtualProtect, and CreateThread. A closer inspection of the call stack reveals that the functions employed from kernel32.dll eventually trigger corresponding functions within the ntdll.dll library. This is facilitated by the ntdll.dll library, which serves …

CheckRemoteDebuggerPresent Anti-Debugging

CheckRemoteDebuggerPresent is a kernel32.dll function that sets (-1)0xffffffff in the DebuggerPresent parameter if a debugger is present. Internally, it also uses NtQueryInformationProcess with ProcessDebugPort as a ProcessInformationClass parameter.

SuspendThread Anti-Debugging

Suspending threads is a technique used by malware to disable user-mode debuggers and make it more difficult for security analysts to reverse engineer and analyze the code. This can be achieved by using the SuspendThread function from the kernel32.dll library or the NtSuspendThread function from the NTDLL.DLL library.

The malware can enumerate the threads of a given process, or …

Reflective DLL injection Process Manipulating

Reflective DLL loading refers to loading a DLL from memory rather than from disk. Windows doesn’t have a LoadLibrary function that supports this, so to get the functionality you have to write your own, omitting some of the things Windows normally does, such as registering the DLL as a loaded module in the process, potentially bypassing DLL load monitoring.

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Tamper DLL Export Names & GetProcAddress Spoofing Process Manipulating

When a process is running, it is possible to change the results of the call to GetProcAddress API, for the exported functions of a module along with modifying the export's offsets and name at runtime.

For example, the offset of kernel32.dll's function VirtualAlloc can be change to the offset of another function. When VirtualAlloc is called (after getting its …

DLL Unhooking Antivirus/EDR Evasion

Endpoint Detection and Response (EDR) tools use a technique known as hooking to monitor sensitive system functions within the DLLs of loaded processes. Hooking is a method of live-patching system DLLs, enabling EDRs to intercept the flow of a program and evaluate its legitimacy.

Here's how it works: EDRs modify the first instructions of the functions within the DLLs. …