What Is A Port Scanning and How to Perform It?

Internet ports are virtual access points used to connect to various devices for transferring data. Open ports allow communication between computers on a particular network. Each port is assigned to a specific service or application that attempts to connect to it. Interaction within the network space is, indeed, crucial, and each port has a distinct purpose, characteristic, and role to perform.

Port scanning online refers to the process of searching for an open port on a computer or network device. Its primary goal is to detect any system threats. An open port could be a threat, as an attacker can gain access to the user's device or network through it. For network administrators, port scanning helps by identifying what ports are open, and what services are linked to them for the purpose of tightening security measures and shutting down open ports.

In the following blocks we will consider what is a port scanning tools and how to use them.

The Specifics of Internet Port Operations

A computer network comprises various ports, each of them numbered between 0 and 65535. Some of them have been classified as common ports for predefined services or applications. Every service, be it a website, email or FTP, has its dedicated port number. To streamline the traffic for different applications on different devices or on the same device, ports are utilized.

Here's how ports on the Internet operates generally:

1. Determination of the destination. Whenever a user inserts a web page address into a browser, a command is sent to the PC’s server IP address.
2. Selection of the target. The command contains a number of the port allocated to the web server such as 80.
3. Probing and routing. When the server procures the request, the server routes it to the correct application which handles that website.
4. Data exchange. The server then provides the information which enables the user to view the particular web page onto their device.

These are some of the more common Internet ports together with the purposes they fulfill:

Indeed, there are more ports than listed here, and some ports might not have services assigned to them at all, while others should never be used at all. Ports not in use are the less common ones, but are still available for a specific purpose.

Methods of Port Scanning

Using port scanning tools is an effective method for discovering open ports. It is an integral part of penetration testing, which aims to evaluate the security of a network. The configure of network devices, allowing segmentation to be a key component of network security needs to be checked as well.

There are many techniques on how to scan open ports, but the simplest ones all start the same, using the IP to identify a target's accessible ports:

• TCP Connect. If the port being scanned is open, a TCP connection will be established for the scan port and will be considered successful. If there is no open port, the scan will get an error which will be displayed to the user.
• SYN. This method involves the sending of an SYN (synchronization) packet to the target port. In case the targeted device has an open port, it will respond with an SYN-ACK (synchronization acknowledgment). The scanning computer then does not send an ACK (acknowledgement) packet which is required to complete the connection establishment. Thus allows knowing which ports are open while significantly reducing the chances of being detected by the target device.
• FIN. In this technique, the scanning device sends a FIN (finished) packet to the target port. In the case the port is closed, the target device should issue a RST (reset) packet in reply. However, if the port is open, the target device may ignore the request or decide not to answer it all together. This has great application in scanning ports of protected networks.
• XMAS and NULL. In these scanning techniques, packets with certain flags are sent. XMAS has all flags set, while NULL has no flags set. If the port is closed, then the expected response from the target device would be an RST packet. Whereas for an open port the response is technically dependent on the implementation of TCP stack.
• UDP. UDP scanning differs from traditional scanning in that a UDP packet is sent to the target port unlike TCP scanning which uses two way communication. Since UDP is a connectionless protocol, the scan relies on the absence of a response or an ICMP unreachable message to infer the port status. This technique is less accurate than TCP scanning for the simple reason that some devices do not respond to open ports.

Port scanning types and methodologies must be based on certain objectives, for example, look for open ports, try to enumerate services, or find any weaknesses in the network. The type of network that is being scanned also matters, be it a local network or the Internet, along with the user's permissions, i.e., whether you are scanning a personal device or someone else’s. Services that check on open ports for users implement some of these methods or a combination of them in order to enhance efficiency and convenience to users.

Use Cases of Network Port Checking

Open port scanning is one of the measures that can be used to protect networks from threats and personal data leaks.

So, what benefits do users get while using port scanning software? The results of port scanning allow users to discover weak points within their systems. For example, a remote access port may be opened and this can be misused to gain unauthorized access to the network. In order to eliminate such attacks, ports that are not required can be closed while known vulnerabilities can be further secured with additional control measures.

Indeed, port scanning is an essential part of network security evaluation because it helps check which ports are open to the outside and evaluate the risk posed by certain services and applications.

Moreover, closed ports that may inhibit the operation of some program or service can lead to connectivity problems, and port scanning helps solve them. Knowing what ports are used helps in optimizing network performance. Remote system control is made easier through public port scan, allowing the administrator to manage the system from a different location securely.

Legal Implications of Port Scanning: Permitted or Prohibited?

Now, let’s answer the question: is port scanning illegal? The legality of port scanning is subject to many considerations such as:

• Having a malicious intent of exploitation can often mark port scanning illegal, however, using it for legitimate purposes such as for authorized network security measures, makes it legal.
• Different countries have different laws regarding cyber activities. In some places, any unauthorized access, including port scanning, might be illegal under computer misuse or cybersecurity laws.
• Executing port scanning becomes legal if the owner of the network permits it. Without permission, even benign scanning might be considered an intrusion.

In practice, it’s safest to perform port scanning only with explicit permission or within an organization’s internal networks to avoid legal issues.

How to Perform Port Scanning

The open ports scanning service enables users to easily and quickly check if there are open ports on their computers or devices. This is essential in protecting your personal information and system security.

You can use our free tool on our website “Port scanner online”, to check the open ports of an IP address or domain. To use the port scanner tool, simply follow these steps below:

Step 1: Enter IP Address or Domain

Type the domain or IP address in the box provided. This field can also be filled automatically by clicking on “Paste my IP address”, which utilizes the tool’s capability to capture the user’s IP while accessing the page.

Step 2: Select Ports to Scan

Select what types of ports will be scanning from the list provided, either from the “Popular Ports” or the “Hidden Ports”.

Step 3: Start the Scan

Once all the information has been provided, press the “Scan” option.

Step 4: View Scan Results

The outcome of the scan will be shown within seconds.

Step 5: Download or Display Results

To make it easier, save the results in a file or view it directly in a new tab.

As a result of the scan, the status of each port that was scanned will be specified:

• Closed ports – these are blocked for incoming connections, which protects the user's device from unauthorized access.
• Open ports – these allow access to specific services, such as those needed for online games or video calls.

Knowing how ports operate is important for the effective and covert usage of the web resources.

Conclusion

Maintaining the security and efficiency of network communications largely depends on gaining and understanding information related to internet ports and their functions. Port scanning enables both individuals and organizations to examine the security of their systems by determining the existence of open ports which may be a potential risk to their networks.

Knowing which ports are open enables the user to take proper action by closing those ports which are unused while increasing the security of the more active ports. Additionally, port scanning tools , as we can see from its definition, help in systematically monitoring the reliability of the network and the safety of information exchange. Given the heightened risks of cyber threats, the information generated from port scans provide an additional layer of defense to an organization’s information systems by allowing administrators to surveil unauthorized access and take action to block port activity that cause potential security breaches. What is important to note, leveraging the capabilities of a port scanners not only enhances network performance but also fortifies the security infrastructure, protecting valuable data and resources.