h4cker/certifications/additional_materials_for_certs/evading_ids_firewalls.md

Techniques for Evading IDS

1. Traffic Obfuscation:

   • Encryption: Encrypting traffic can prevent IDS from inspecting the payload. For example, using tools like Stunnel or OpenVPN to encrypt data streams.
   • Encoding: Encoding payloads in formats like Base64 or using URL encoding can obscure the content. For example, encoding an SQL injection payload to bypass detection filters.

2. Fragmentation:

   • Packet Fragmentation: Breaking malicious payloads into smaller packets can evade detection by causing IDS to miss reassembled payloads. Techniques like IP fragmentation or TCP segmentation can be used.

3. Polymorphism and Metamorphism:

   • Polymorphic Code: Altering the code structure without changing its functionality to evade signature-based detection. For example, changing variable names or code layout.
   • Metamorphic Code: Completely rewriting the code to avoid signature detection. This involves transforming the code into a different form while maintaining the same behavior.

4. Protocol Manipulation:

   • Protocol Tunneling: Encapsulating malicious traffic within legitimate protocols. For instance, using HTTP or DNS tunneling to bypass IDS inspection.
   • Protocol Abuses: Exploiting protocol features to hide malicious payloads. For example, using malformed packets or unusual protocol behaviors.

Techniques for Evading Firewalls

1. Port Knocking:

   • Description: A technique where an attacker sends a sequence of connection attempts to closed ports. If the correct sequence is detected, the firewall temporarily opens a port for the attacker.

2. IP Spoofing:

   • Description: Forging the source IP address to make traffic appear as if it comes from a trusted source. This can bypass IP-based filtering rules in firewalls.

3. Tunneling:

   • Description: Encapsulating malicious traffic within a legitimate protocol or using VPNs to bypass firewall rules. Techniques like SSH tunneling or VPNs can obscure the real nature of the traffic.

4. Use of Allowed Ports:

   • Description: Exploiting commonly allowed ports (e.g., HTTP on port 80) to deliver malicious payloads. This involves disguising the payload as legitimate traffic to bypass firewall filtering.