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Writing Custom Port Scanners

Explore how to develop custom port scanners using Python Scapy by modifying TCP flags to perform SYN, ACK, XMAS, FIN, and NULL scans. Understand the behavior of open and closed ports through different scan responses and learn to accurately interpret scan results for effective network security analysis.

SYN scan alternatives

We’ve successfully developed a SYN scanner in Scapy. This type of scanner takes advantage of the structure of the TCP handshake. If a port is open, it will respond to a SYN packet with a SYN/ACK.

However, SYN scans are far from the only type of port scanning. Some other options include:

  • TCP connect scan

  • ACK scan

  • XMAS scan

  • FIN scan

  • NULL scan

Performing an ACK scan

Now, ...