Masscan is fastest Internet port scanner. It can scan the entire Internet in under 6 minutes, transmitting 10 million packets per second.
Uses a custom TCP/IP stack. Anything other than simple port scans will cause
conflict with the local TCP/IP stack.
By default, masscan scans at a rate of 100 packets per second,
which is quite slow. To increase that, simply supply the -rate option and specify a value.