Masscan

What it is

A C program that sends SYN packets at very high rates and tracks replies asynchronously. It can scan large IPv4 ranges in minutes and write results in Greppable, XML, JSON, or binary formats.

What it helps with

- Sweeping huge IP ranges for a few open ports
- Finding newly exposed services across an estate
- Producing Nmap-compatible output for deeper checks
- Banner grabbing on selected ports after discovery

Who it's for

Pentesters, red teams, and network defenders scanning networks they own or are authorized to assess.

Worth knowing

It needs root privileges for raw packets and can overwhelm networks or remote systems, so set a safe rate and stick to authorized scopes. The latest tagged release is older than the active code on the main branch.

How is it different from Nmap?
Nmap does deeper service and OS checks, while Masscan focuses on very fast discovery of open ports.

What should I run after it?
In our view Naabu or Nmap are natural next steps to confirm and classify the open ports it finds.