In session hijacking (TCP hijacking), attackers steal a web user’s active session by acquiring their unique session ID. This lets them impersonate the user, accessing data or performing actions as if they were the legitimate user. The breach disrupts the session and poses significant risks to personal and organizational data security.
A session hijacking attack allows bad actors to gain access to a server without authentication. After the session is hijacked, the attacker no longer needs to authenticate as long as the session remains active. This grants the attacker an equivalent level of server access as the compromised user, given that the user had previously undergone server authentication prior to the attack.
What is a session?
A session represents a sequence of exchanges between two communication points within a single connection. When a user logs into an application, the server establishes a session to preserve the user’s context for subsequent requests made by that user. Applications use sessions to store user-specific parameters and information. These sessions remain active on the server for the duration of the user’s login session. The session gets terminated when the user logs out or after a predefined period of user inactivity. Upon session termination, any user data stored in the allocated memory space should be removed as well.
A session ID is a unique identification code, typically long, randomized alpha-numeric string. It serves as a means of communication between the client and the server. These session IDs are often stored in various places such as cookies, URLs, and concealed fields within web pages.
How does Session Hijacking work?
Session hijacking is often executed by various methods, and some of the most common culprits include:
- Session Sniffing: One of the most basic methods for application layer session hijacking, attackers employ sniffers (i.e. Wireshark) or proxies, such as OWASP Zed, to intercept and “sniff” session data as it is transmitted between the user and the server. This allows them to use a token to capture valuable session information.
- Predictable Session Token ID: When websites generate session token IDs using easily predictable patterns or variables, it becomes easier for attackers to guess or deduce these IDs, gaining unauthorized access.
- Man-in-the-Browser: This type of attack is like a man-in-the-middle attack but requires the initial infection of the victim’s computer with a Trojan. Once installed, the malware waits for the victim to visit a targeted site. It can covertly modify transaction details and initiate additional transactions without the user’s knowledge. Since the requests originate from the victim’s device, detecting fraudulent requests becomes challenging for the web service.
- Cross-Site Scripting (XSS): The attacker takes advantage of weaknesses within web applications to inject malicious scripts into web pages visible to other users. This can result in the theft of session details and subsequent session hijacking.
- Session Sidejacking: In this scenario, attackers intercept session data while it’s in transit, often exploiting weak encryption or lack of encryption to gain access to the user’s session.
- Session Fixation: Attackers trick users into using a predetermined session ID, enabling them to take control of the session once the user logs in.
Session hijacking attacks are typically targeted at networks that experience heavy traffic, where numerous communication sessions are active simultaneously. The abundance of ongoing sessions not only offers the attacker a multitude of opportunities to carry out their exploits but can also provide a cloak of concealment for the attacker amidst the bustling activity on the server.
How to prevent Session Hijacking
When a user undergoes authentication, SSL and secure cookies should be obligatory. Furthermore, once authenticated users access one or more secure web pages, they should consistently be compelled to employ HTTPS.
There are several actions you can undertake to enhance the prevention of session hijacking:
- Steer clear of public Wi-Fi networks. Whenever feasible, refrain from utilizing public Wi-Fi, particularly for critical activities such as banking, online shopping, or accessing private email or social media accounts. There’s a possibility that a nearby cybercriminal might be employing packet sniffing techniques to intercept your session cookies.
- When in doubt, opt for a VPN. If you find yourself needing to connect via a public Wi-Fi network, employing a virtual private network (VPN) can significantly enhance your security. A VPN conceals your IP address and maintains the confidentiality of your online actions by establishing a secure “private tunnel” through which all your online activity securely traverses. This safeguards your sessions and keeps cybercriminals at bay.
- Keep your security software up to date. Install reputable security software on your devices and make sure to update it regularly. Security software can protect you from the malware that cybercriminals hijack sessions.
- Keep an eye out for potential scams. Session hijackers can send you an email with a link to click. Unless you have verified an email is from a legitimate sender, avoid clicking on any links that it may contain. Malicious links can download and install malware on your device or take you to a login page where you may inadvertently sign in to a site that is using a session ID created by the cybercriminal.
- Check for website security. When you find yourself on an unfamiliar website or online shop, it’s prudent to remain vigilant as their security measures may not be
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