Masscan
Masscan is a high-performance network scanner designed to scan large IP address ranges quickly. It’s often compared to Nmap, but it’s significantly faster due to its asynchronous transmission engine. Here's a detailed breakdown of how Masscan works and what makes it unique:
Core Features of Masscan
1. Speed:
- Masscan is capable of scanning the entire IPv4 address space in minutes.
- It uses its own TCP/IP stack, allowing it to send packets asynchronously and at extremely high rates.
2. Port Scanning:
- Primarily used for TCP port scanning.
- It can detect open ports on remote systems, similar to Nmap’s SYN scan.
3. Custom TCP/IP Stack:
- Masscan bypasses the OS’s networking stack, which allows it to send packets faster and avoid kernel limitations.
- This also means it can behave differently than traditional scanners and may require tuning for compatibility.
4. Output Formats:
- Supports multiple output formats including XML, JSON, and grepable text.
- Can be configured to output results compatible with Nmap for further analysis.
How Masscan Works
- SYN Scan: Sends TCP SYN packets to target IPs and ports. If a SYN-ACK is received, the port is considered open.
- Rate Control: You can control the scan rate using the --rate parameter to avoid overwhelming networks.
- IP Range Scanning: Supports CIDR notation and lists of IPs.
- Exclusion Lists: You can exclude IPs or ranges to avoid scanning sensitive or protected networks.
Common Usage Examples
Important Considerations
- Legal and Ethical Use: Scanning networks without permission can be illegal or unethical. Always ensure you have authorization.
- Firewall and IDS Evasion: Due to its speed, Masscan can trigger alerts or be blocked by intrusion detection systems.
- System Requirements: High-speed scanning may require elevated privileges and tuning of system parameters (e.g., increasing ulimit, adjusting NIC buffers).
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