NMAP, also known as Network Mapper, is a free and open-source tool that is commonly used by systems and network administrators to discover hosts, services, and open ports in their networks. It was developed by Gordon Lyon and is quite robust in providing network security audits among other functionalities.
After you’ve downloaded and installed NMAP, scanning your local network is straightforward. Here is the basic syntax to scan a local network:
```
nmap [Scan Type] [Options] {target specification}
```
The target specification part can be an IP address, hostname, or IP range. For example, `nmap 192.168.1.1-254` would scan a local network where the devices have IP addresses in the range of 192.168.1.1 to 192.168.1.254.
There are various types of scan options that you can use to tailor to your needs. Let’s say you want to do a ping sweep which means you are checking which hosts are alive on the network, you can perform such a task with the `-sn` option. For example: `nmap -sn 192.168.1.1-254` The `-sn` option tells nmap to send a ping request to each IP address in the specified range, and then provides a list of IP addresses of machines that responded.
Perhaps you’re interested in checking for open ports on a specific machine: `nmap p 192.168.1.1` This command tells NMAP to do a port scan `-p-` which specifies all 65535 ports followed by the IP address of the host you want to examine.
It’s important to note that some scans may require root privileges to run, such as SYN scan or OS detection. You’d need to prepend the nmap command with `sudo`.
Use it responsibly and be aware that indiscriminate scanning can be perceived as aggressive and potentially in violation of network usage policies or even laws.
Supporting resources for NMAP:
1. “NMAP” on Wikipedia – https://en.wikipedia.org/wiki/Nmap
2. “NMAP Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning” by Gordon Lyon.
3. “How to use NMAP” on GeeksforGeeks – https://www.geeksforgeeks.org/how-to-use-nmap/
4. Nmap Documentation – https://nmap.org/docs.html
In conclusion, NMAP is a powerful tool for system and network administrators to audit their network’s security and discover hosts, services, and open ports. The command syntax is flexible and allows for a wide range of scans to fit your specific needs. Gain a thorough understanding of how to use the tool and always use it ethically.
