Nmap scans break down into different phases. When we are working with a large list of hosts, we can save up time by skipping tests that return information we don't need. By carefully selecting our scan flags, we can significantly improve the performance of our scans.
This recipe explains the process that takes place behind the curtains when scanning, and how to skip certain phases in order to speed up long scans.
To perform a full port scan with the timing template set to aggressive, and without the reverse DNS resolution or ping, use the following command:
# nmap -T4 -n -Pn -p- 74.207.244.221
The command we just used gives us the following output:
Nmap scan report for 74.207.244.221 Host is up (0.11s latency). Not shown: 65532 closed ports PORT STATE SERVICE 22/tcp open ssh 80/tcp open http 9929/tcp open nping-echo Nmap done: 1 IP address (1 host up) scanned in 60.84 seconds
Compare the running time that we got against a full...