BypassAV : Techniques To Evade Antivirus And EDR Systems

BypassAV refers to the collection of techniques and tools used to bypass antivirus (AV) and Endpoint Detection and Response (EDR) systems.

These security solutions are designed to detect and block malicious activities, but attackers continuously develop methods to evade them. Below is an overview of key techniques and tools used in bypassing AV and EDR systems.

Key Techniques For Bypassing AV And EDR

1. Obfuscation
   Obfuscation involves altering the appearance of malicious code to avoid detection. This can include renaming variables, randomizing character cases, or using tools like Invoke-Obfuscation. These changes ensure that signature-based detection systems fail to recognize the malware.
2. Recompiling
   Attackers modify and recompile malware in different programming languages or add non-functional code. This alters the hash of the file, making it appear as a new, undetected file to static analysis tools.
3. Encoding and Encryption
   Encoding or encrypting malicious payloads ensures that their intent remains hidden until runtime. This method bypasses static analysis by making the code unreadable until executed.
4. AMSI Bypass
   The Anti-Malware Scan Interface (AMSI) scans scripts and memory for malicious payloads. Attackers bypass AMSI by disabling or tampering with its scanning capabilities, often targeting PowerShell scripts or .NET applications.
5. Reflective DLL Loading
   This technique loads malicious DLLs directly into memory without touching the disk, evading disk-based detection mechanisms.
6. Unhooking Processes
   EDR systems use hooks to monitor processes. Attackers “unhook” these processes to render their activities invisible to the monitoring system.
7. Living Off The Land (LotL)
   LotL involves abusing legitimate tools like PowerShell or WMI to execute malicious actions, blending into normal system activities and avoiding detection.
8. Retrosigned Drivers
   This advanced method abuses expired digital signatures to load malicious drivers, often combined with system time manipulation.

Best Practices For Ethical Use

While these techniques are valuable for penetration testers and red teams, they must be used responsibly within legal boundaries. Open-source tools are often flagged by AV systems due to their Indicators of Compromise (IOCs).

Therefore, manual implementation of bypass techniques is recommended for ethical testing.

BypassAV serves as a critical resource for understanding evasion tactics, enabling security professionals to strengthen defenses against evolving threats.