Session hijacking, also known as cookie hijacking, is a type of cyber attack where an attacker exploits a valid computer session or session key to gain unauthorized access to information or services in a computer system. In particular, it is used to refer to the theft of a magic cookie used to authenticate a user to a remote server. Session hijacking is commonly used against client authentication on the internet, and it can have serious consequences for application security because it allows attackers to gain unauthorized access to protected accounts and the data they contain by masquerading as a legitimate user.

Session hijacking can be carried out in several ways, including:

• Session Sniffing: An attacker uses a sniffer to capture a valid session token and then uses the token to gain unauthorized access to the web server.

• Predictable Session Token: Websites use algorithms based on easily predictable variables, such as time or IP address, to generate session IDs, causing their session IDs to be predictable. Attackers can compromise the session token by stealing or predicting a valid session token to gain unauthorized access to the web server.

• Client-side attacks: Attackers can use client-side attacks such as cross-site scripting, malicious JavaScript codes, Trojans, etc. to compromise the session token.

• Man-in-the-middle attack: Attackers can eavesdrop on network traffic to steal the targets session ID.

Once the attacker has obtained the session ID, they can take over the session without detection. Session hijack attacks are usually carried out against busy networks with a high number of active communication sessions, providing the attacker with a large volume of sessions to exploit and giving the attacker a measure of protection.

To defend a network against session hijacking, a defender has to implement security measures at both the application level and network level. Some ways to prevent session hijacking include:

• Using encryption (typically SSL) to protect session IDs transmitted in the clear.

• Implementing secure session management techniques, such as using unpredictable session IDs, session timeouts, and session encryption.

• Using secure communication protocols, such as Transport Layer Security (TLS) and Secure Sockets Layer (SSL) .

Session hijacking is a serious threat to networks and web applications on the web, as most systems are vulnerable to it.