This lecture dives into two of the most powerful and commonly misunderstood scan types: TCP ACK and TCP SYN (half-open) scanning. Rather than just explaining what they are, this video explores exactly how TCP state manipulation works, how firewalls respond, and how you can use response patterns to reverse-engineer firewall rules.

Covered in depth:

• TCP ACK scan behavior: what responses mean in different network contexts

• Using ACK scans to map firewall rule sets without triggering alarms

• SYN scan (also known as stealth scan): how it works and why it’s effective

• How stateful firewalls treat SYN vs ACK flags

• Reading Nmap output in combination with Wireshark or TCPDump for better interpretation

• Techniques to make scans harder to detect by IDS/IPS systems