CPU Counting Sandbox Evasion

In many sandboxes, due to virtualization constraints, the number of CPUs may be limited to one. However, in the real world, all x86 CPUs have been sold with multiple cores or at least hyperthreading for over a decade.

As a result, it is sometimes possible to detect virtualization or sandboxing by examining the number of CPUs on the system. …

Hide Artifacts: Process Argument Spoofing Defense Evasion [Mitre]

Adversaries may attempt to hide process command-line arguments by overwriting process memory. Process command-line arguments are stored in the process environment block (PEB), a data structure used by Windows to store various information about/used by a process. The PEB includes the process command-line arguments that are referenced when executing the process. When a process is created, defensive tools/sensors that monitor …

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 …

Debugger Evasion Defense Evasion [Mitre]

Adversaries may employ various means to detect and avoid debuggers. Debuggers are typically used by defenders to trace and/or analyze the execution of potential malware payloads.

Debugger evasion may include changing behaviors based on the results of the checks for the presence of artifacts indicative of a debugged environment. Similar to Virtualization/Sandbox Evasion, if the adversary detects a debugger, …

Process Argument Spoofing Process Manipulating

Process Argument Spoofing is a technique used by attackers to hide their true intentions by changing the command line arguments of a process after it has started.

IsDebuggerPresent Anti-Debugging

This function checks specific flag in the Process Environment Block (PEB) for the field IsDebugged which will return zero if the process is not running into a debugger or a nonzero if a debugger is attached.

If you want to understand the underlying process of IsDebuggerPresent API you can check the code snippet section for the following method: IsDebugged …

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.

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 …

ProcEnvInjection - Remote code injection by abusing process environment strings Process Manipulating

This method allows to inject custom code into a remote process without using WriteProcessMemory - It will use the lpEnvironment parameter in CreateProcess to copy the code into the target process. This technique can be used to load a DLL into a remote process, or simply execute a block of code.

The lpEnvironment parameter in CreateProcess allows us to …

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