Writing Custom Port Scanners

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, we’ll adapt our existing SYN scanner to other scan types. To start, let’s take a look at our SYN scanner code: