What is the default scanning behavior of Nmap?
Understand the Problem
The question is asking about the default scanning behavior of the Nmap tool, which is commonly used for network discovery and security auditing. It is looking for an understanding of how Nmap typically operates without any specific options or configurations.
Answer
Nmap defaults to SYN scan; uses connect scan if privileges are insufficient.
The default scanning behavior of Nmap is to perform a SYN scan. If the user does not have the necessary privileges to send raw packets, Nmap defaults to a connect scan. This fallback can also occur if IPv6 targets are specified, as SYN scans require root access on Unix systems.
Answer for screen readers
The default scanning behavior of Nmap is to perform a SYN scan. If the user does not have the necessary privileges to send raw packets, Nmap defaults to a connect scan. This fallback can also occur if IPv6 targets are specified, as SYN scans require root access on Unix systems.
More Information
SYN scan, also known as half-open scanning, is widely used due to its efficiency and stealth. It allows a scanner to gather information about open ports without establishing a full TCP connection, which can help in avoiding detection by firewalls.
Tips
A common mistake is assuming that Nmap will always perform a SYN scan. However, it requires administrative privileges, so users without such privileges will experience a fallback to different scan methods like the connect scan.
Sources
- Nmap default scan technique - Information Security Stack Exchange - security.stackexchange.com
- Port Scanning Techniques - Nmap - nmap.org
- TCP SYN (Stealth) Scan (-sS) | Nmap Network Scanning - nmap.org
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