Port scan

The port scanner tool

Using the port scanner tool, you can scan any server, host or firewall for open ports available from the Internet. The tool scans about 60 of the most common ports.

The tool will also probe some of the most common protocols - ie the tool will initiate a communication and display the information that comes back. This applies to DNS, HTTP, HTTPS, SMTP, FTP, POP3 and the like.

Using the tool, you can learn many valuable things about a given server. The tool scans and reveals all passively available information about the server: Which protocols it communicates via, which services it makes available, which types of software it runs and in some cases even version numbers of the individual server programs.

This is extremely valuable information - whether you want to protect your network or want to see what your competitor is doing.

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Samples

Port scan 'dns.google' Port scan 'www.db4free.net' Port scan 'ftp.gnu.org' Port scan 'iamroot.tech'

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What is port scanning used for?

As you may sense, port scanning can be used in several different ways. So the application of this method and this tool depends on your point of view. Here I will only describe the application options for you as a system administrator.

As an administrator of a server, you want to make sure that only the absolutely necessary ports are open. Each open port constitutes an attack vector. So as an administrator you should be completely aware of which ports are open on your server and why they are open. This is essential in keeping your server secure.

You should also be aware if some of your server applications send version info back on a simple probe. If a malicious attacker can see that you have an outdated FTP server running, it is an obvious place to attack. You should therefore turn off these kinds of messages - it serves no purpose to share that information.

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Is port scanning legal?

Yes! Although it may be controversial, there is nothing illegal or wrong about port scanning.

In the same way that port scanning can be used as an attack to detect weaknesses, it is also one of the best ways to secure and validate one's own server.

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There are open ports on my machine - what do I do?

The easiest solution is to make services accessible from the Internet inaccessible through your firewall.

Next, you should look into what kind of software you have running with these open ports - and how you limit them.