Session Hijacking

What Is a Session Hijacking Attack?

Session Hijacking is an attack type in which a user's session is taken over by an attacker. A session starts when a user logs into a service, for example, an application, and ends when the session is logged out. Depending on the attacker's knowledge about your session cookie, the attack is also referred to as cookie theft or session sidejacking. While session hijacking can occur for any computer session, it is most commonly relevant to browser sessions and web applications.

How Does a Session Hijacking Attack Work?

Session Hijacking occurs when an attacker exploits an already active session by stealing HTTP cookies, which are used to maintain most web sessions. Another way is for the attacker to successfully guess an active session by using a specific user's credentials to gain unauthorized access to information on a remote web server. Session tokens or the security of HTTP headers can be manipulated, including session sniffing and cross-site scripting (XSS) attacks.

How to Recognize a Session Hijacking Attack?

Session hijacking is often challenging to detect unless the presence of the attacker is brought to the system's attention. During an attack, a user may notice a few signs. For instance, the client application or Telnet may become unresponsive or freeze during an attack. Another sign is a brief spike in network activity that slows down your computer.

Another common indication is that the client application hangs for a while due to competition with the attacker sending data to the server. This causes the program to become confused and wait for a response from the 4th layer. However, normal and even advanced computer users rarely report these symptoms because they are similar to other common issues such as application crashes, busy servers, or network congestion.

How to Protect Against It?

Protection against DNS tunneling requires an advanced network threat prevention system that can detect and block data theft attempts in this endeavor. Such a system would need to monitor network traffic and identify malicious content that can be embedded in DNS traffic.

Some session hijacking attack types include:

There are two main types of Session Hijacking: Application Layer Hijacking and Transport Layer Hijacking. Application layer hijacking occurs when an attacker steals or successfully guesses the session identifier needed to hijack a session. This type of session hijacking primarily appears in sessions that use HTTP. Two examples of Application Layer Attacks include Man in the Middle and proxy-based attacks. On the other hand, proxy attacks occur when an attacker captures the session identifier during the course of the session by causing network traffic to pass through a proxy that they've set up. Transport Layer hijacking occurs in TCP sessions and disrupts the communication channel between the client and the server, rendering data exchange impossible. Thus, the attacker can essentially take over the session. IP spoofing allows the attacker to communicate with computers on the network. Blind Hijacking is an attack where the attacker interrupts the communication during a session and sends their malicious data or commands.

How to Protect Against Session Hijacking Attacks:

Use HTTPS to ensure that all session traffic is encrypted using SSL/TLS encryption. This prevents an attacker from interfering with plaintext session identifiers even if they are monitoring the user's traffic. Prevent access to identification information from client-side scripts by setting the HttpOnly attribute using the Set-Cookie HTTP header. This helps prevent XSS and other attacks that rely on injecting JavaScript into the browser. It is also recommended to specify the Secure and SameSite directives for added security. Web servers can generate long and random session identification tokens, reducing the likelihood of guessing a competitor's identifier. Implement end-to-end encryption between the user's browser and the web server to prevent unauthorized access to the session identifier. VPNs can be used for full encryption, not just for web server-bound traffic, using personal VPN solutions. Automatically log out a session when it ends, and require the user to reauthenticate using a different session identifier.