How do I use masscan for banner grabbing without crashing my network?

Assign masscan a separate IP address on your local subnet using --source-ip, or firewall its source ports with iptables/pf to prevent conflicts with your system's TCP/IP stack, as detailed in the README's configuration steps. This avoids RST packets that kill connections during banner retrieval.

Masscan vs nmap: which should I use for scanning a large corporate network?

Use masscan for initial, high-speed reconnaissance of open ports across vast IP ranges due to its async design and custom stack. Switch to nmap for in-depth analysis of discovered hosts, as nmap excels at service detection, scripting, and single-target scanning but is slower for wide scans.

Can masscan scan the entire Internet without getting blocked?

Technically yes with --max-rate, but it's discouraged; always use --excludefile to blacklist sensitive ranges and avoid overloading targets. The README warns that parts of the Internet react badly, and you may be firewalled, so ethical use and exclusions are critical.

How to output masscan results in JSON format for automation?

Use the -oJ flag or --output-format json with --output-filename to save scans in JSON. This format is machine-readable and easily integrated into databases or pipelines, similar to nmap's XML but with masscan's async structure.

What protocols does masscan support for banner checking?

It supports 12 protocols: FTP, HTTP, IMAP4, memcached, POP3, SMTP, SSH, SSL, SMBv1, SMBv2, Telnet, RDP, and VNC, as listed in the README. This is sufficient for basic service identification but lacks extensibility for custom protocols.

Is masscan safe to run on my local network?

Yes, but with caution: use --router-mac for testing to keep packets local, and start with low rates like --rate 1000 to avoid melting your network. The README notes that masscan randomizes targets to distribute load, but misconfiguration can still cause congestion.

Open-Awesome

Masscan

AGPL-3.0C1.3.2

An Internet-scale TCP port scanner that can scan the entire Internet in under 5 minutes using asynchronous SYN packets.

GitHub

25.8k stars3.2k forks0 contributors

What is Masscan?

MASSCAN is a high-performance, asynchronous TCP port scanner built for scanning massive IP ranges at extreme speeds. It uses its own custom TCP/IP stack to send SYN packets asynchronously, capable of scanning the entire Internet in under 5 minutes. The tool solves the need for rapid, large-scale network reconnaissance, particularly for security researchers and network administrators mapping open ports across vast address spaces.

Target Audience

Network security professionals, penetration testers, and researchers who need to perform fast, wide-ranging port scans across entire subnets or the global Internet. It's also suitable for organizations conducting large-scale network inventory or vulnerability assessments.

Value Proposition

Developers choose MASSCAN for its unparalleled speed and scalability in port scanning, leveraging asynchronous I/O and kernel-bypass techniques to achieve millions of packets per second. Its nmap-compatible interface lowers the learning curve, while features like built-in banner grabbing, IPv6 support, and PF_RING integration make it a robust tool for Internet-scale scanning tasks.

Overview

TCP port scanner, spews SYN packets asynchronously, scanning entire Internet in under 5 minutes.

Use Cases

Best For

Rapidly scanning entire IP ranges for open ports across the Internet
Performing large-scale network reconnaissance for security audits
Mapping attack surfaces of organizations with vast subnet ranges
Conducting research on global service distribution and port availability
Integrating port scanning into automated security assessment pipelines
Testing network device performance under high packet-rate conditions

Not Ideal For

In-depth vulnerability assessment of individual hosts requiring service fingerprinting and script interaction
Environments where kernel-bypass networking is prohibited or overly complex to configure
Small-scale internal network scans where the setup overhead for avoiding TCP/IP stack conflicts outweighs the speed benefits
Projects needing real-time, interactive scanning with extensive protocol support beyond the 12 built-in banners

Pros & Cons

Pros

Unmatched Scanning Speed

Leverages asynchronous transmission and a custom TCP/IP stack to achieve rates up to 10 million packets per second, enabling Internet-wide scans in minutes, as highlighted in the README's performance claims.

Nmap-Compatible Interface

Uses familiar command-line syntax and output formats (XML, JSON, grepable) to reduce the learning curve for network professionals, with options like --echo for configuration reuse.

Built-in Banner Grabbing

Completes TCP connections to retrieve application banners for 12 protocols including HTTP, SSH, and SSL, adding value beyond mere port detection without external tools.

IPv4 and IPv6 Coexistence

Scans both address families simultaneously without special modes, simplifying dual-stack reconnaissance, as demonstrated in usage examples with mixed IP ranges.

Cons

Complex Banner Configuration

Requires assigning a separate IP address or intricate firewall rules to prevent conflicts with the system's TCP/IP stack, adding operational overhead and risk of network disruption, as warned in the README.

Limited Protocol Support

Only supports banner checking for a fixed list of 12 protocols, lacking the extensive service detection, version scanning, and scripting engine of tools like nmap for deeper analysis.

No DNS Resolution

Scans must target IP addresses directly, as MASSCAN does not resolve domain names, which complicates scanning dynamic or named hosts and reduces usability for ad-hoc tasks.

Cross-Performance Inconsistency

Achieves significantly lower packet rates on Windows and macOS (around 300,000 packets/second) compared to Linux (1.6 million packets/second), limiting efficiency in heterogeneous environments.

Open Source Alternative To

Masscan is an open-source alternative to the following products:

Nmap

Nmap (Network Mapper) is a free and open-source network discovery and security auditing tool used for network exploration, management, and security scanning.

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