What is port scanning and how to perform it

Internet ports are virtual gateways used for network connections, facilitating data transfer between devices. Open ports enable communication between computers on a network. Each port is associated with a specific service or application that listens for incoming connections. Ports are crucial for interaction within the network space and have unique operational characteristics and purposes.

Port scanning is the process of identifying open ports on a computer or network device. Its primary objective is to uncover system vulnerabilities. Attackers may exploit open ports to compromise a user's device or network. By conducting a port scan, you can determine which ports are open and the services they are associated with, allowing you to enhance security measures and close off vulnerable ports.

The specifics of Internet port operations

In a computer network, each port is assigned a specific number ranging from 0 to 65535. Some of these ports are well-known and designated for standard services. Every service, whether it's a website, email, or FTP, is linked to its unique port number. Different ports help efficiently manage and distribute traffic among various services and applications, whether they're running on the same device or across different devices.

Here’s how Internet ports generally operate:

1. Destination determination: when a user types a website address into their browser, the computer sends a request to the server's IP address.
2. Target selection: the request includes the port number associated with the web server, typically port 80.
3. Routing: upon receiving the request, the server directs it to the appropriate application that serves the site.
4. Data exchange: the server transfers the information, allowing the user to receive the requested web page.

Here are some of the most popular Internet ports and their purposes:

This is a brief overview of the most relevant ports; the full list is much more extensive. Other ports may be utilized by less common services or assigned by the user for specific purposes.

Methods of port scanning

Internet port scanning is crucial for detecting open ports and identifying vulnerabilities, helping to ensure network security. It allows for the identification of potential entry points for hackers and aids in analyzing the configuration of network devices.

Here are several common port scanning methods, each with its own specific uses and suited for different purposes:

• TCP Connect. This method sends a TCP connection to each scanned port. If the port is open, the connection will be established, and the scan will return a successful result. If the port is closed, the target device will send an error message, and the scan will return the corresponding failure.
• SYN. This method sends a SYN (synchronization) packet to the target port. If the port is open, the target device will respond with a SYN-ACK (synchronization acknowledgment). However, the scanning computer does not send an ACK (acknowledgment) packet to complete the connection establishment. This allows for identifying open ports while reducing the chance of being detected by the target device.
• FIN. In this method, the scanning device sends a FIN (finished) packet to the target port. If the port is closed, the target device should send a RST (reset) packet in response. If the port is open, the target device may either not respond or ignore the request. This method is particularly useful for scanning ports within protected networks.
• XMAS and NULL. These scanning methods send packets with specific flags, where XMAS has all flags set, and NULL has all flags turned off. If the port is closed, the target device will send a RST packet. However, if the port is open, the response may vary depending on the TCP stack implementation.
• UDP. Unlike TCP, UDP scanning attempts to send a UDP packet to the target port. 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. However, this method can be less reliable than TCP, as some devices may not send any response for open ports.

When selecting a port scanning method, it's important to consider the goals of the scan, such as identifying open ports, pinpointing services, and searching for vulnerabilities. You should also consider the type of network being scanned—whether it's a local or an Internet network—and the availability of access rights, determining whether you are scanning your device or someone else’s. Various online checkers utilize these methods or a combination of them to offer users a faster and more convenient way to check for open ports.

Use cases of network port checking

Checking open ports is an essential security tool that helps secure the user’s network and protect against potential threats and personal data leaks.

Port scanning results enable users to pinpoint vulnerable areas in their systems. For instance, an open port meant for remote access could potentially allow unauthorized access to the network. To prevent such attacks, unnecessary ports can be closed or additional security measures can be implemented to mitigate known vulnerabilities.

Port scanning is crucial for assessing network security as it enables the analysis of externally accessible ports, highlighting potential vulnerabilities in services and applications.

Furthermore, port scanning aids in identifying connectivity issues, which may arise from closed ports that disrupt program or service functionality. Understanding which ports are used can optimize network settings for improved performance. Additionally, port scanning facilitates remote access control, ensuring that only authorized individuals can access the system remotely.

How to perform port scanning

The open ports scanning service provides a quick and easy way for users to determine which ports are open on their computer or device. This is an important step in ensuring the security of your system and personal data.

You can use our free tool on our website “Port scanner online”, to check the open ports of an IP address or domain. Here’s how to get started with the IP port scanner:

1. Enter the IP address or domain you want to check. You can automatically fill in this field by using the “Paste my IP address” option, as the tool automatically detects the user’s IP when visiting the page.

   

2. Choose the type of ports you want to scan from the drop-down list—either “Popular ports” or “Hidden ports”.

   

3. After entering the information, click on the “Scan” button.

   

4. The results of the scan will be displayed within a few seconds.

   

5. For added convenience, you can download the results by saving the file or displaying it in a new browser tab.

   

As a result of the scan, the status of each scanned port will be indicated:

• 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.

Understanding how ports function is crucial for efficiently and securely using Internet resources.