Scanning open ports with nmap

​nmap tool is good free tool to scan for open network ports.

Some of the network ports will be opened for system to operate. For example it is expected that port 80 or port for HTTP traffic will be opened at the web server.

However if this port is opened at a system which does not need to be serving web traffic it may indicate misconfiguration of that system.

Having extra ports opened at a system which doesn’t require these may indicate a misconfiguration of that system and higher utilization of that system.

It may also indicate malicious activity.

nmap tool has several way which scan will be performed and how that scan will be performed. Please refer to the documentation of nmap tool for details.

Before scanning of network ports, an explicit permission from the owner of these systems must be received. Otherwise it can be treated as malicious activity, and can even be punished by judicial system.

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