Transmission control protocol (TCP)

The Transmission Control Protocol (TCP) is a fundamental protocol within the suite of Internet Protocol (IP) standards.

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The Transmission Control Protocol (TCP) is a fundamental protocol within the suite of Internet Protocol (IP) standards. It is a connection-oriented protocol that provides a reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts communicating via an IP network. TCP is the backbone of data communication on the world wide web, email, file transfer, and other high-reliability applications.

Understanding TCP is crucial in the field of cybersecurity. As a cybersecurity professional, you need to know how TCP works, how it can be exploited, and how to secure it. This glossary entry will provide a comprehensive understanding of TCP, its functions, its vulnerabilities, and its role in cybersecurity.

History of TCP

The development of TCP dates back to the early 1970s, when the Advanced Research Projects Agency Network (ARPANET) was looking for a way to interconnect different networks. Vinton Cerf and Robert Kahn, two computer scientists, designed TCP as a way to ensure reliable communication over unreliable networks. The protocol was first standardized in 1981 and has been updated several times since then.

Over the years, TCP has proven to be a robust and adaptable protocol. It has been able to accommodate the rapid growth of the internet and the increasing complexity of network applications. Despite its age, TCP remains one of the most important protocols in use today.

Development of TCP

The development of TCP was a significant achievement in the history of networking. It was the first protocol to provide a reliable, end-to-end connection over an unreliable network. This was a major breakthrough at the time, as it allowed for the reliable transmission of data over long distances.

The design of TCP was influenced by the need for a protocol that could handle a wide range of network conditions. This led to the inclusion of features such as error detection and correction, flow control, and congestion control. These features have contributed to the robustness and reliability of TCP.

How TCP works

TCP works by establishing a connection between two hosts on a network. This connection is used to send a stream of bytes from one host to the other. TCP ensures that these bytes arrive in the correct order and without errors.

The process of establishing a TCP connection involves a three-way handshake. The initiating host sends a SYN packet to the receiving host, which responds with a SYN-ACK packet. The initiating host then sends an ACK packet to complete the handshake. Once the handshake is complete, data can be sent over the connection.

TCP header

The TCP header contains information that is used to manage the TCP connection. This includes the source and destination port numbers, the sequence number, the acknowledgment number, the data offset, the reserved bits, the control bits, the window size, the checksum, the urgent pointer, and the options.

The source and destination port numbers identify the sending and receiving applications. The sequence number and acknowledgment number are used to ensure that the bytes are delivered in the correct order. The data offset indicates the start of the data in the TCP segment. The control bits are used to manage the connection. The window size is used for flow control. The checksum is used for error detection. The urgent pointer is used to indicate urgent data. The options field is used for optional features.

TCP three-way handshake

The TCP three-way handshake is a crucial part of the TCP protocol. It is the process by which a TCP connection is established between two hosts. The handshake involves the exchange of three packets: a SYN packet, a SYN-ACK packet, and an ACK packet.

The initiating host sends a SYN packet to the receiving host. This packet contains the initiating host's initial sequence number. The receiving host responds with a SYN-ACK packet, which contains the receiving host's initial sequence number and an acknowledgment of the initiating host's sequence number. The initiating host then sends an ACK packet to acknowledge the receiving host's sequence number. Once this process is complete, the TCP connection is established, and data can be sent over the connection.

TCP in cybersecurity

Understanding TCP is crucial in the field of cybersecurity. TCP is used in many different types of attacks, including denial of service attacks, man-in-the-middle attacks, and TCP hijacking. By understanding how TCP works, cybersecurity professionals can better defend against these attacks.

One of the most common types of TCP attacks is the SYN flood attack. In this attack, an attacker sends a large number of SYN packets to a target host, causing it to exhaust its resources and become unresponsive. This is a type of denial of service attack.

TCP vulnerabilities

Like any protocol, TCP has its vulnerabilities. One of the most well-known vulnerabilities is the sequence number prediction vulnerability. This vulnerability allows an attacker to predict the sequence numbers used in a TCP connection, which can lead to a variety of attacks, including session hijacking and data injection.

Another vulnerability is the TCP reset attack. In this attack, an attacker sends a TCP reset packet to a target host, causing it to terminate the TCP connection. This can be used to disrupt communication between two hosts.

Securing TCP

There are several ways to secure TCP. One of the most effective ways is to use a firewall. A firewall can filter incoming and outgoing TCP connections based on a set of rules. This can prevent unauthorized connections and protect against many types of TCP attacks.

Another way to secure TCP is to use encryption. Encryption can protect the data sent over a TCP connection from being intercepted and read by an attacker. This is especially important for sensitive data, such as passwords and credit card numbers.

Conclusion

TCP is a fundamental protocol in the suite of Internet Protocol standards. It provides a reliable, ordered, and error-checked delivery of a stream of bytes between applications running on hosts communicating via an IP network. Understanding TCP is crucial in the field of cybersecurity, as it is used in many different types of attacks.

Despite its vulnerabilities, TCP remains one of the most important protocols in use today. By understanding how TCP works and how to secure it, cybersecurity professionals can better defend against attacks and protect their networks.

This post has been updated on 17-11-2023 by Sofie Meyer.

Author Sofie Meyer

About the author

Sofie Meyer is a copywriter and phishing aficionado here at Moxso. She has a master´s degree in Danish and a great interest in cybercrime, which resulted in a master thesis project on phishing.

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