Hijack Execution Flow: KernelCallbackTable Defense Evasion [Mitre]

Adversaries may abuse the KernelCallbackTable of a process to hijack its execution flow in order to run their own payloads. The KernelCallbackTable can be found in the Process Environment Block (PEB) and is initialized to an array of graphic functions available to a GUI process once user32.dll is loaded.

An adversary may hijack the execution flow of a process …

kernel flag inspection via sysctl Anti-Debugging

The sysctl anti-debugging technique can be abused by malware to detect and evade debugging tools on macOS or BSD-like systems. By querying the kernel for process information, malware checks flags (e.g., 0x800) to see if a debugger is attached. If detected, the malware can terminate, alter behavior, or enter a dormant state to avoid analysis.

This technique blends …

Clearing Kernel Message Anti-Forensic

The dmesg -C command clears the kernel message buffer, which stores diagnostic messages generated by the kernel. These messages include logs about hardware interactions, system events, kernel module loads, and errors such as segmentation faults. The attacker can run this command to make sure that no trace of kernel-related activity, including any anomalies caused by exploitation, remains in the message …

NtSetDebugFilterState Anti-Debugging

The NtSetDebugFilterState and DbgSetDebugFilterState functions are used by malware to detect the presence of a kernel mode debugger. These functions allow the malware to set up a debug filter, which is a mechanism that can be used to detect and respond to the presence of a debugger.

When a kernel mode debugger is present, the debug filter will be …

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 …

IN Sandbox Evasion

The IN instruction is a type of machine code instruction that is used to read data from an input port. This instruction can only be executed in privileged mode, such as in kernel mode, and an attempt to execute it in user mode will generate an exception.

However, some virtual machine monitors, such as VMWare, use a special port …

Bypassing Static Heuristic Antivirus/EDR Evasion

Dynamic heuristic engines are implemented in the form of hooks (in user-land or kernel-land) or based on emulation. User-land hooks (HIPS) can be easily bypass by malware by patching back the entry point of the hooked function. For kernel-land hook, malware has to run in kernel space by installing a driver or abusing a kernel-level vulnerability.

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.

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 …

GetTickCount Anti-Debugging

This is typical timing function which is used to measure time needed to execute some function/instruction set. If the difference is more than fixed threshold, the process exits.

GetTickCount reads from the KUSER_SHARED_DATA page. This page is mapped read-only into the user mode range of the virtual address and read-write in the kernel range. The system clock tick updates …

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