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Antivirus Evasion

Techniques used by malware to bypass detection by traditional antivirus solutions.

Understanding Antivirus Evasion


Antivirus evasion is a critical challenge in cybersecurity, as malware authors continuously develop new techniques to bypass detection. Traditional AV solutions rely on signature-based and heuristic detection, but modern malware employs obfuscation, polymorphism, and in-memory execution to remain undetected.

Techniques Used in Antivirus Evasion


1. Fileless Malware

  • Executes malicious code directly in system memory without creating files on disk.

  • Uses built-in tools like PowerShell, Windows Management Instrumentation (WMI), and Registry scripts.

  • Difficult to detect since it does not leave artifacts on the file system.

2. Polymorphic and Metamorphic Malware

  • Polymorphic Malware: Constantly modifies its code while retaining its original functionality to avoid signature-based detection.

  • Metamorphic Malware: Rewrites its code entirely each time it propagates, making it even harder to identify.

  • Examples include ShapeShifter and Storm Worm, which continuously evolve to bypass security measures.

3. Process Injection Techniques

  • Injects malicious code into legitimate system processes to evade detection.

  • Common methods include:

    • DLL Injection: Inserts a malicious Dynamic Link Library (DLL) into a legitimate process.

    • Process Hollowing: Replaces the memory of a trusted process with malicious code.

    • Atom Bombing: Uses Windows atom tables to inject code without triggering AV alerts.

4. Sandbox and Virtual Machine Detection

  • Malware detects when it is running in a sandbox or virtual machine (VM) and alters its behavior to avoid analysis.

  • Techniques include:

    • Checking for virtualization artifacts (e.g., VMware, VirtualBox).

    • Monitoring system uptime to avoid execution in fresh environments.

    • Delaying execution until user interaction is detected.

Common Applications of Antivirus Evasion


Advanced Persistent Threats (APTs)

  • Used by nation-state actors and cybercriminal groups to maintain long-term access to targeted systems.

  • Avoids detection through stealthy, persistent malware.

Ransomware Attacks

  • Modern ransomware strains employ evasion techniques to bypass security controls before encrypting files.

  • Example: Ryuk ransomware uses process injection to execute without being flagged by AV software.

Trojan Horse Attacks

  • Malware disguises itself as legitimate software while executing malicious activities in the background.

  • Uses code obfuscation and encryption to remain undetected.

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