As technology and information systems have developed, you may have heard the term “port,” even if you don’t work in fields like information processing, network security, or systems expertise, or have no relationship with technology beyond being an end user. When it comes to information processing and technology, many concepts and technologies inevitably come into play. Among these concepts, the term “port” is perhaps one of the most important, especially concerning security. A port is a technology that facilitates communication between computers, acting as a bridge in this communication. Just like phone numbers enable people to communicate with each other, computers use dynamic or static IP addresses to communicate with each other over the internet.
The English term “port,” which can be translated into Turkish as “liman,” differs from the phone number example in that it comes after the IP address, following a colon (“:”), with a value ranging from 0 to 65535, where each value represents a specific purpose, enabling communication between two computers or devices. Ports, essential for data exchange and communication, are fundamentally divided into two categories: TCP and UDP.
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What is TCP?
TCP, or Transmission Control Protocol, is a type of port that provides not only data exchange between computers but also authentication. Developed by the U.S. Department of Defense to prevent data loss in computer-to-computer communication, TCP can be described with a relatable example: it is similar to sharing data via Bluetooth, AirDrop, or WhatsApp from your smartphone. You share the data you need to share, and you have complete control over your phone. Popular communication protocols today, such as HTTP, HTTPS, POP3, SSH, SMTP, TELNET, and FTP, utilize the TCP protocol, each with its unique number ranging from 0 to 65535.
What is UDP?
UDP, or User Datagram Protocol, is a type of port primarily developed for audio and video communication. Unlike TCP, UDP does not have the responsibility of ensuring data integrity and authentication, making it faster but less reliable than TCP. A simple analogy would be that using TCP is like lending your phone to a friend to watch a video or listen to music; while you don’t have your phone, your friend could access all your private information if they had malicious intent.
Differences Between TCP and UDP
The differences between TCP and UDP can be summarized as follows:
- TCP: Provides data integrity and authentication, making it slightly slower than UDP but more reliable. It sends data in packets in order.
- UDP: Faster than TCP due to the lack of data integrity and authentication, making it less reliable. It does not manage data flow.
What is the Purpose of a Port?
In a single sentence, a port allows multiple purposes for data exchange between computer IP addresses. Each purpose is assigned a different port number, enabling simultaneous connections. For instance, while using a personal computer to browse a website, one can keep an email application open to check for new emails while listening to a song online, all thanks to ports.
How is a Port Used?
To understand how a port is used, one must first grasp the relationship between a port and an IP address. An understandable analogy is that while IP addresses represent the location of a house, ports are like the entry doors, garage doors, windows, or chimneys of that house. Unlike a house, each entry has a unique number, so to access a specific entry, the port number must be appended to the IP address, as in “192.168.1.1:12345.” Using a port is quite simple: first, obtain the IP address of the computer you want to connect to, then get the port number for the desired communication protocol.
Some programs, like FTP clients such as Filezilla or SSH/Telnet communication programs like Putty, have default port numbers embedded in their code, so you only need to input the IP address to use them. However, default ports are not always guaranteed, as port forwarding can change this.
What is Port Forwarding?
Port forwarding is a process that changes the direction of a communication protocol, meaning it alters the port number or stops the communication protocol. Despite the term “forwarding,” it is more accurate to refer to this process as port control. With port forwarding, open ports on an IP address can be closed, closed ports can be opened, or open ports can be changed to a different port number for cybersecurity reasons.
What Purpose Does Each Port Serve?
Here are some commonly used ports and their purposes:
| Port Name | Port Number | Port Type | Intended Use |
|---|---|---|---|
| FTP | 21 | TCP | File Transfer |
| SSH | 22 | TCP | Secure Shell |
| TELNET | 23 | TCP | Telnet |
| SMTP | 25 | SMTP | Email Sending |
| DNS | 53 | TCP and UDP | Domain Name System |
| TFTP | 69 | TCP | File Transfer |
| HTTP | 80 | TCP and UDP | Internet Access |
| HTTPS | 443 | TCP | Secure Internet Access |
| POP3 | 110 | POP3 | Email Retrieval (Download) |
| IMAP | 143 | TCP | Email Retrieval (Synchronously) |
| NTP | 123 | TCP | Network Time Protocol |
How to Check a Port?
To easily check a port, you can use online services that perform port checks via IP addresses. Alternatively, you can do it through the command prompt on your computer by following these steps:
- Click the Start menu and type “command prompt” or “cmd” to open the command prompt application.
- In the opened window, type the command “telnet [IP address] [port number]” (e.g., telnet 192.168.1.1 80) to check if the port is open.
- You can see the open ports of an IP address using the command “netstat -an.” This command will show both the local and external codes of the port.
Cybersecurity and Ports
Cyber attacks are a significant issue in the information technology world, leading to the emergence of the concept of cybersecurity. Cybersecurity is a complex system that cannot be explained in just a few sentences. However, it can be said that port forwarding is part of cybersecurity. In home or office networks, some ports are open by default, while others must be opened for certain features to function. Hackers can exploit open ports to attack a computer or network. The most basic and straightforward way to prevent this is through port forwarding.
Port forwarding can be categorized into three subtypes: local, remote, and dynamic. Local port forwarding is the most commonly used type due to its security. Remote port forwarding allows all users on a remote server to connect to a single TCP protocol, commonly used for connecting to web servers. Dynamic port forwarding is the least used type compared to the other two, although it is intended to secure users on a public network.
How to Perform Port Forwarding Against Cyber Attacks?
Port forwarding can be performed even on home modem devices. The first thing to know for port forwarding is the modem’s IP address, which is usually 192.168.1.1. While opening, closing, or forwarding certain ports is easy in home network setups, it is often inadequate for ensuring cybersecurity in corporate networks. IT professionals in corporate networks are aware of this and utilize advanced security firewalls to ensure cybersecurity.
Modems and routers provided by internet service providers are typically basic devices designed solely for internet flow. Therefore, while using these devices for internet access is straightforward, ensuring security can be challenging. In corporate environments, IT professionals use products developed by custom brands, which specialize in cybersecurity and network management. These products allow for proactive measures against potential cyber attacks, including port forwarding.
Frequently Asked Questions
The port you want to activate can be easily activated from the management panel of a device like a modem, router, or firewall. If the device is in Turkish, look for the port forwarding menu; if in English, it will be under the NAT (Network Address Translation) menu or directly in the Port Redirection menu.
Port opening operations performed on network management devices are usually instantaneous.
The best way is to contact your internet service provider.
Port 80 is the port used for HTTP connections to access the internet. All devices that provide internet access use port 80.
Various tools are available for port scanning. The most common method is to use the Nmap scanner.
A port scanning attack is a type of cyber attack that connects to a network system and detects open and vulnerable ports.
In network systems, ports are usually categorized as open, closed and filtered. People who want to organize a port attack on a network check the ports with a scanner such as Nmap and prepare to organize an attack through open ports.
The first and most common answer to the question of how to prevent a port scanning attack is to close ports. It is especially important to pay attention to ports 23 (Telnet), 445 (SMB), 110 (POP3), 80 and 8080 (HTTP), as they will try to carry out port attacks through these ports.
Of course, although closing a port is the most definitive solution, since some ports are in use, closing these ports may disrupt the workflow and network system. In this case, the second action to be taken to prevent port attacks is port forwarding. With port forwarding, the open port is filtered and some kind of precaution can be taken.
In order to keep the ports open and ensure security without any problems, what needs to be done is to provide proactive protection. In order to do this, it is extremely important to combine Network Packet Broker, Network Tap and Network Bypass Switches correctly and to analyze network traffic well.
What should not be forgotten in the implementation of the measures to be taken to prevent port attacks is to benefit from the advanced and reliable firewall devices and stable software of companies that produce solutions to cyber attacks.
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