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 …

Obfuscated Files or Information: Dynamic API Resolution Defense Evasion [Mitre]

Adversaries may obfuscate then dynamically resolve API functions called by their malware in order to conceal malicious functionalities and impair defensive analysis. Malware commonly uses various Native API functions provided by the OS to perform various tasks such as those involving processes, files, and other system artifacts.

API functions called by malware may leave static artifacts such as strings …

Thwarting Stack-Frame Analysis Anti-Disassembly

Thwarting Stack-Frame Analysis is a technique used by malware to make it more difficult for security analysts to reverse engineer and analyze the code. A stack frame is a collection of data associated with a function, including local variables, arguments passed to the function, and the return address. Disassemblers can use information from the stack frame to understand a function's …

Modify Authentication Process: Reversible Encryption Defense Evasion [Mitre]

An adversary may abuse Active Directory authentication encryption properties to gain access to credentials on Windows systems. The AllowReversiblePasswordEncryption property specifies whether reversible password encryption for an account is enabled or disabled. By default this property is disabled (instead storing user credentials as the output of one-way hashing functions) and should not be enabled unless legacy or other software require …

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 …

NixImports Packers

A .NET malware loader employs API-Hashing and dynamic invocation to circumvent static analysis. NixImports utilizes managed API-Hashing to dynamically determine most of its required functions during runtime. For function resolution, HInvoke needs two specific hashes: typeHash and methodHash, representing the type name and the method's full name, respectively. At runtime, HInvoke scans the entire mscorlib to locate the corresponding type …