Often during Nmap scanning techniques, you will find the port state as either open or filtered
What exactly is the difference between two ?
- Closed Port: If you send a SYN to a closed port, it will respond back with a RST.
- Filtered Port: Presumably, the host is behind some sort of firewall. Here, the packet is simply dropped and you receive no response (not even a RST).
- Open Port: If you send a SYN to an open port, you would expect to receive SYN/ACK.