Unloading Module with FreeLibrary Antivirus/EDR Evasion

Malware authors often use various techniques to evade detection by AV/EDR solutions. One such technique involves checking for the presence of AV/EDR DLLs that may be loaded in the malware's address space and attempting to unload them before executing their malicious code.

To do this, the malware first uses the GetModuleHandleA function to retrieve a handle to the DLL, …

ScrubCrypt Packers

ScrubCrypt is a malware obfuscation and encryption framework, derived from the earlier JLaive Batchfuscator crypter. It is designed to aid cybercriminals in evading detection and analysis by using a variety of techniques to conceal and protect the malicious software.

ScrubCrypt is advertised on cybercrime forums to employ encryption, code morphing, and (allegedly) polymorphism to create obfuscated malware payloads that …

FuncIn Antivirus/EDR Evasion Anti-Debugging Anti-Disassembly Anti-Forensic

FuncIn involves a payload staging strategy wherein the entire set of malicious functionalities is not contained within the malware file itself or any third-party file/network location (e.g., a web server). Instead, these functionalities are transmitted over the network by the Command and Control (C2) server when required.

This approach addresses three primary issues in malware development. Firstly, it mitigates …

SIDT, Red Pill Sandbox Evasion

Red Pill is a technique used by malware to determine whether it is running on a physical machine or a virtual machine. The Red Pill technique involves executing the SIDT instruction, which retrieves the value of the Interrupt Descriptor Table Register (IDTR) and stores it in a memory location.

On a physical machine, the IDTR will contain the address …

VPCEXT Sandbox Evasion

The VPCEXT instruction (visual property container extender) is another anti–virtual machine trick used by malware to detect virtual systems. This technique is not documented. If the execution of the instruction does not generate an exception (illegal instruction), then the program is running on a virtual machine.

Checking Recent Office Files Sandbox Evasion

Another way to detect if the malware is running in a real user machine is to check if some recent Office files was opened.

Checking Installed Software Sandbox Evasion

By detecting the presence of certain software and tools commonly used in sandbox environments, such as Python interpreters, tracing utilities, debugging tools, and virtual machine software like VMware, it is possible to infer the existence of a sandbox.

This inference is based on the premise that such tools are often found in sandbox setups used for dynamic malware analysis …

Detecting Hostname, Username Sandbox Evasion

Most sandbox are using name like Sandbox, Cuckoo, Maltest, Malware, malsand, ClonePC.... All this hostname can provide the information to the malware. The username can also be checked by malware.

Detecting USB Drive Sandbox Evasion

To detect whether a program is running in a sandbox environment, malware can look for the presence of USB drives. Many sandboxes do not have USB ports or do not allow access to USB drives, and detecting the absence of USB drives can help identify whether the program is being run in a sandbox.

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.

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