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Masscan Guide: High-Speed Network Scanner

Learn Masscan for high-speed network scanning with millions of packets per second, covering options, output formats, and practical scanning examples.

#masscan#network scanning#port scanning#high-speed#large-scale

Why You Need Masscan

You need to scan thousands or millions of IPs for open ports — Masscan transmits packets at rates Nmap cannot match, covering the entire IPv4 Internet on a single port in minutes. It is purpose-built for large-scale reconnaissance where speed matters more than stealth.

Prerequisites

  • Understanding of TCP/IP networking
  • Knowledge of network interface configuration
  • Authorization for any networks scanned

    • How Masscan Works

    Asynchronous Scanning: Does not wait for responses before sending next probes.

    Randomized Scanning: Scans in random order to avoid detection.

    Rate Control: Precise control over packets per second.

    Installation

    sudo apt install masscan

    Basic Usage

    sudo masscan 192.168.1.0/24 -p80,443
sudo masscan 192.168.1.0/24 -p1-1000 --rate=1000

    Essential Options

    | Option | Description |

    |--------|-------------|

    | -p PORTS | Ports to scan |

    | --rate=PPS | Packets per second |

    | --banners | Grab banners |

    | -oJ FILE | JSON output |

    | -oB FILE | Binary output |

    | --excludefile | Exclude IP ranges |

    Practical Examples

    sudo masscan 192.168.1.100 -p0-65535 --rate=10000
sudo masscan 192.168.1.0/24 -p80,443,8080,8443 --rate=5000
sudo masscan 192.168.1.0/24 -p22,80,443 --banners --rate=5000

    Output and Conversion

    sudo masscan 192.168.1.0/24 -p80 --rate=1000 -oB scan.bin
masscan --readscan scan.bin -oX scan.xml

    Rate Setting

    Home/Office: 100-1000 pps. Data Center: 10000-50000 pps. Internet: 100000-1000000 pps.

    Common Mistakes

    Not using rate limiting. Scanning without exclude file. Forgetting root privileges.

    Best Practices

    Use binary output for resumability. Test rate settings. Combine with Nmap for detailed enumeration.

    Related Tools

  • **Zmap**: Another high-speed scanner
  • **ZGrab**: Application-layer data grabber

    • Related Articles

  • [Nmap Beginner Tutorial](/articles/nmap-beginner-tutorial)
  • [Network Scanning with Nmap](/articles/network-scanning-nmap-beginners)

    • Summary

    Masscan is the fastest port scanner available. Key strengths are speed and Nmap-compatible output. Requires careful rate control.

    Knowledge Check

  • Why does Masscan require root?
  • What is binary output for?
  • How to convert to Nmap format?
  • What to use to exclude IPs?
  • What rate for home network?

    • Frequently Asked Questions

    What is Masscan?

    Masscan is the fastest port scanner available, capable of scanning the entire IPv4 address space on a single port in under 5 minutes. It uses asynchronous scanning and randomized probe ordering to achieve millions of packets per second.

    Why does Masscan require root privileges?

    Masscan crafts raw TCP/IP packets at the transport layer using its own custom stack, which requires root access. Without root, it cannot send or receive raw packets needed for high-speed scanning.

    What is binary output used for?

    Binary output (`-oB scan.bin`) stores scan results in a compact format that supports resumability. If a scan is interrupted, Masscan can continue from where it left off with `--readscan scan.bin`.

    How do you convert Masscan output to Nmap format?

    Use `masscan --readscan scan.bin -oX scan.xml` to convert binary output to XML, then parse it with Nmap or import into tools like Metasploit and Nessus.

    How do you exclude IP ranges from scanning?

    Use `--excludefile excludes.txt` with one IP range per line, or `--exclude 10.0.0.0/8` for inline exclusion. This prevents scanning internal or exempted ranges.

    What packet rate should I use on a home network?

    Start with 100-500 pps on home/office networks. Higher rates (10000-50000 pps) are suitable for data centers. Always test incrementally to avoid triggering IDS or crashing network equipment.

    How does Masscan differ from Nmap?

    Masscan prioritizes speed over accuracy using asynchronous scanning, while Nmap provides detailed service detection and OS fingerprinting. Use Masscan for discovery, then Nmap for deep enumeration of found hosts.

    What does the --banners flag do?

    The `--banners` flag makes Masscan grab service banners from open ports, revealing software versions. It adds a small delay per port for the banner exchange but provides valuable intelligence.

    How do you resume an interrupted Masscan scan?

    Masscan automatically saves state. If interrupted, rerun the same command and it resumes from the checkpoint. You can also manually resume with `--readscan` on the binary output file.