Open ports: check a port is open? - Open Port

Open ports: check a port is open?

Let’s talk about open ports, and check a port is open, will start with TCP and IP, check if open ports are risky, and learn how to check for open ports.

IP is a very common term and frequently used in conversations relating to computers and networks. IP stands for Internet Protocol, this address allows you to have access to the internet network, and every device has its own IP address.

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Open Ports | Image by Tumisu from Pixabay

The IP works to deliver or receive information through an internet network. The information that needs to be transmitted is broken into chunks, and these chunks are called “packets.” The packets have two parts, one that consists of the destination and the other, the data that needs to be transmitted. An alternative to IP packets is TCP which transmits data without breaking it.

What are TCP-IP ports?

TCP or Transmission Control Protocol smoothen communication between the IP and an application program, like the web browser or E-mail. This communication service helps with the easy transfer of information. Whenever any application program, like the web browser or e-mail, sends data, it can request the TCP to conduct the transmission. TCP will then take care of the IP path and will also not break the data into packets.

To use TCP communication services, devices also need to use TCP ports. These ports are endpoints that specify the service and host in a network. There are unique numbers that uniquely identify every port. Thus, these port numbers are important to identify and differentiate the IP services among all the other IP services in a network. The port number for web services (HTTP) is 80 and for mail service (SMTP) is 25. So, every data packet related to mail services will be directed to port 25, and for web services, it will be port number 80.

The port numbers can also increase the security level of, say, an intranet network. If you do not want anyone to use this private network to do any web browsing, then set a firewall that will prohibit every information packet with port 80 as a destination from any transmission.

Are open ports risky?

Open ports are a way to communicate throughout the internet network. Many times it is heard that open ports are not safe, and it should be closed. But as it helps communicate, it is not the best decision to close the ports thinking open ports are risky and dangerous.

Open ports become risky and unsafe when the port listening has poor security protocols or is exposed to exploits, unpatched, and is incorrectly configured. Open ports do not mean risk. Instead, it is the services and applications that may expose them to danger. The way you use the open ports plays a major role in labeling these ports as risky and dangerous or not.

The only reason why people go for closed ports over open ones is that there are fewer attacks on the former. The open ports are prone to attacks because the attackers require vulnerability. And an open port with poor security rules becomes an easy target for attackers. Publicly open ports make it easy to run exploits.

Why keep a check on open ports?

As mentioned above, that if you want to prevent any external browsing in your intranet, you prevent this by creating a firewall in port 80. This clarifies that open ports can affect a network or organization’s availability, integrity, and confidentiality.

These three are the reasons to keep an eye on the open ports.

  • Availability-

When you use open ports to run services and applications, apart from your traffic, the open ports also process other incoming traffic. This increases the chances of denial-of-services attacks. The DoS attack prevents the user from using the network anymore. For any organization, if their system crashes, it will cost them both money and time.

  • Integrity-

If there is no proper control over open ports, it is easy for different malware types to enter into the system. The software will get hold of a candidate port and use it to communicate without any disturbance or hindrance.

  • Confidentiality-

Both the applications’ listening and open ports can put the confidentiality of the network and system at risk. The risk is leakage of information such as software version, banners, system type, and content.

Monitoring and controlling open ports is an important task but is assumed to be a difficult one too. But, it is not that difficult. If you have a small network where only a few devices run, closing ports is quite simple. The task becomes time-consuming with larger networks.

The solution to this tedious and time-consuming task is using monitoring technologies that will keep managing and monitoring these open ports. The reason these technologies can scan the ports is that the open ports use public internet networks. The monitoring platforms will report to you about the open ports with no services and ones whose identity is unknown.

How to check a port is open?

If there is any problem in the system due to open ports, you might want to scan and look through these ports. Another scenario where you might want to check an open port is to check which other service is running through it.

You can check the open port using the command prompt and some freeware applications. Below the steps are mentioned, and it will work on every version of windows, using the netstat command line tool.

  1. Viewport with process names

This shows how to view a port and also to view the name of the current process running.

  • First, the command prompt needs to be run in administrator mode. For this, go to the start option or press the Windows key. In the search box type, “command prompt.” Once it is visible, right-click on it and then click on run as administrator.
  • On the next dialog box, type, netstat-ab, and hit Enter.
  • It takes few minutes to load, and once it is loaded, scroll through the list and find your open port and, you will also be able to view the process name.
  1. Viewport with process identifiers

If the process name against the port number is of not much help, maybe try these steps to view the process identifiers (PIDs).

  • First, run the command prompt as administrator using the same steps mentioned above.
  • Type netstat-aon in the dialog box that appears and press enter.
  • On the far right column of the display, you will find the PIDs.
  • The next step is to open the task manager by right-clicking anywhere in the taskbar.
  • In the task manager dialog box, click the details or processes tab depending on your windows version.
  • Next, sort the list based on PIDs and find more information in the description column.
  • On right-clicking on your port process and choosing open file location, you will be able to locate the file and the app the port is involved with.

Knowing about open ports and how to scan and check them will help with solving network issues. You can identify the process and even end the process to run any other process using the open port. Having the right information will help maintain a secure private network or keep the organization safe from attacks.


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