Virtual Private Networks (VPNs) are used to create a secure connection to another network over the Internet. Often, network administrators and security personnel employ network analysis and scanning tools to ensure the safety and effectiveness of these VPNs. NMAP is one such tool and is recognized in the industry for its efficiency and versatility.
NMAP (Network Mapper) is a free and open source utility used by IT professionals for network discovery and security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime (Source: NMAP.ORG).
To analyze VPN services with NMAP, one must understand how to use NMAP for simple tasks like host discovery to more complex and advanced uses like port scanning and OS detection.
Firstly, after installing NMAP, you can run a simple Ping Scan to check whether the host (VPN service) is active or not. This can be done with the command `nmap -sn [IP address or hostname]` (Source: NMAP.ORG).
Second, perform a basic port scan to check the open ports on the host system. This can be accomplished using the command `nmap p [IP address or hostname]`. This will show all 65535 ports. If you know which ports you are interested in, you can specify them: `nmap -p [port range] [IP address or hostname]` (Source: NMAP.ORG).
Third, after identifying open ports, you can run a service and version detection. Using the command `nmap -sV [IP address or hostname]`, NMAP will interact with the open ports and try to identify the service running and the version of that service (Source: NMAP SCANNING THE INTERNET).
Fourth, to delve deeper and identify the Operating System in use, you can utilize the OS detection feature by running `nmap -O [IP address or hostname]`. It is interesting to note that this command must be run with root privileges because it uses SYN packets instead of ICMP packets to identify the OS (Source: NMAP SCANNING THE INTERNET).
Fifth, a script scanning can be done to gather more granular details. This can be performed using the command `nmap —script=default [IP address or hostname]`. The default scripts of NMAP cover a wide range of tests and parameters (Source: NMAP.ORG).
Keep in mind these steps are for general purposes only. NMAP offers dozens of advanced commands and scans that you can use based on your specific needs and nature of testing.
Remember that, while NMAP is a powerful tool, it must be used responsibly and ethically. Unauthorized network scanning can lead to severe penalties and is considered illegal in many jurisdictions.
Sources:
1. https://nmap.org/book/man.html
2. https://nmap.org/book/man-examples.html
