What is Session Hijacking & How to Prevent it?

A session hijacking attack occurs when an attacker takes control of your internet session, such as while you're checking your credit card balance, paying bills, or shopping online. The majority of session hijackers target browser or web application sessions.

 

A session hijacking attacker can then do anything on the site that you can do. In essence, a hijacker deceives the website into believing they are you. Just as a hijacker can take over an airplane and endanger the passengers, a session hijacker can take over an internet session and cause major problems for the user.

 

 

What is Session Hijacking?

 

Session hijacking is a type of security attack on a user session that occurs over a secure network. When an attacker uses source-routed IP packets to insert commands into an active communication between two nodes on a network and disguise itself as one of the authenticated users, this is known as IP spoofing. Because authentication is typically performed only at the beginning of a TCP session, this type of attack is possible.

 

An attacker hijacks a user session in a session hijacking attack. A session begins when you log into a service, such as your banking app, and ends when you log out. Because the attack is dependent on the attacker's knowledge of your session cookie, it is also known as cookie hijacking or cookie side-jacking. Although any computer session can be hijacked, browser sessions and web applications are the most commonly hijacked.

 

When you log into a web application, the server usually places a temporary session cookie in your browser to remember that you are currently logged in and authenticated. HTTP is a stateless protocol, and the most common way for the server to identify your browser or current session is through session cookies, which are attached to every HTTP header.

 

An attacker must know the victim's session ID in order to hijack a session (session key). This can be obtained by stealing the session cookie or convincing the user to click on a malicious link that contains a pre-prepared session ID. 

 

After the user has been authenticated on the server, the attacker can hijack the session by using the same session ID as their own browser session. The server is then tricked into believing that the attacker's connection is the original user's valid session

 

A session hijacker can control a user's session in a variety of ways. One common method is to use a packet sniffer to intercept user-server communication, allowing the hacker to see what information is being sent and received. They can then use this information to access sensitive data or log in to the account.

 

Session hijacking can also be accomplished by infecting the user's computer with malware. This grants the hacker complete access to the machine, allowing them to hijack any active sessions.

 

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How does Session Hijacking Work?

 

There are numerous types of session hijacking attacks, and we'll go over them in detail . But first, let's go over how session hijacking works:

 

1. Hijacking a session Step 1: A careless internet user logs into an account. The user may access a bank account, a credit card site, an online store, or any other application or site. In the user's browser, the application or site places a temporary "session cookie." 

 

This cookie contains information about the user that enables the site to keep them authenticated and logged in while also tracking their activity during the session. The session cookie remains in the browser until the user logs out or is logged out automatically.

 

2. Hijacking a session Step 2: A criminal gains access to a valid internet session. Cybercriminals use a variety of methods to steal sessions. Many common types of session hijacking involve stealing the user's session cookie, locating the session ID within the cookie, and then using that information to hijack the session. 

 

A session ID is also referred to as a session key. The criminal can take over the session without being detected if they get the session ID.

 

3. Hijacking a session Step 3: The session hijacker receives a monetary reward for stealing the session. Once the original internet user has left, the hijacker can use the ongoing session to commit a variety of heinous crimes. 

 

They can steal money from the user's bank account, buy items, steal personal information to commit identity theft, or encrypt important data and demand a ransom ‌for its return.

 

When an attacker convinces a server or website that they are an allowed user, this is known as session hijacking. There are several types of session hijacking, but they ‌go like this:

 

1. An authorized user accesses an online account (for example, their bank account). After that, the site places a "session cookie" in the user's browser. This contains the user's session ID, which keeps the user authenticated and allows them to interact normally with the website.

 

2. An attacker steals the user's session ID while they are connected to the site. They then use this session ID to sign in as the authenticated user to the website without being detected.

 

3. The attacker can then use the user's bank account to steal money. An attacker may be able to purchase something, steal their identity, or steal and encrypt data for a ransom on other sites.

 

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Methods for Session Hijacking

 

Depending on the attack vector and the attacker's position, attackers have numerous methods for session hijacking. The first broad category includes cookie-interception attacks:

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Methods of Session Hijacking

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1. Cross-Site Scripting

 

Cross-site scripting (XSS) is the most dangerous and common method of web session hijacking. Attackers can inject client-side scripts (typically JavaScript) into web pages by exploiting server or application vulnerabilities, causing your browser to execute arbitrary code when it loads a compromised page. 

 

Injection scripts can gain access to your session key if the server does not set the HttpOnly attribute in session cookies, providing attackers with the necessary information for session hijacking.

 

2. Session side jacking

 

The first thing that comes to mind when people think of "being hacked" is this type of attack, which requires the attacker's active participation. Attackers can monitor the user's network traffic and intercept session cookies after the user has authenticated on the server using packet sniffing. 

 

If the website only uses SSL/TLS encryption for the login pages and not for the entire session, the attacker can hijack the session and impersonate the user to perform actions in the targeted web application using the sniffed session key.  

 

Because the attacker requires access to the victim's network, common attack scenarios involve unsecured Wi-Fi hotspots, where the attacker can either monitor traffic in a public network or set up their own access point and exploit the victim's network to perform man-in-the-middle attacks. 

 

3. Session fixation

 

The attacker may simply supply a known session key and trick the user into accessing a vulnerable server to discover the victim's cookie. There are many methods for accomplishing this, such as using HTTP query parameters in a crafted link sent via email or provided on a malicious website.

 

For example: When the victim clicks the link, they are taken to a valid login form, but the attacker supplies the session key. After authentication, the attacker can hijack the session using the known session key.

 

Another method of session fixation is to trick the user into filling out a specially designed login form that contains a hidden field containing the fixed session ID. 

 

More advanced techniques include using a cross-site scripting attack to change or insert the session cookie value or directly manipulating HTTP header values (which requires access to the user's network traffic) to insert a known session key using the Set-Cookie parameter.

 

4. Cookie theft via Malware or Direct Access

 

Installing malware on the user's machine to perform automated session sniffing is a common method of obtaining session cookies. Once installed, the malware scans the user's network traffic for session cookies and sends them to the attacker, for example, after the user visits a malicious website or clicks a link in a spam email. 

 

Another method is to directly access the cookie file in the client browser's temporary local storage (often called the cookie jar). Again, malware can perform this task, but so can an attacker with local or remote access to the system.

 

5. Brute Force

 

The attacker can use brute force to ‌guess the session key of a user's active session, which is only possible if the application uses short or predictable session identifiers. 

 

Sequential keys were once a common weakness, but with modern applications and protocol versions, session IDs are long and generated randomly. To avoid brute force attacks, the key generation algorithm must generate truly unpredictable values with enough entropy to make guessing attacks impractical.

 

 

How to Prevent Session Hijacking

 

There are many things you can do to help protect yourself online. Take the following precautions to help prevent session hijacking and improve your online security:

 

1. Avoid using public Wi-Fi. Never use public Wi-Fi for sensitive transactions such as banking, online shopping, or logging into email or social media accounts. A cybercriminal at the next table may use packet sniffing to collect session cookies and other information.

 

2. Make use of a VPN. If you must use public Wi-Fi, invest in a virtual private network (VPN) to protect yourself and keep session hijackers out of your sessions. A VPN conceals your IP address and protects your online activities by establishing a "private tunnel" through which all of your online activity passes.

 

3. Include security software. Install reliable security software on your devices and keep it up to date. (You can also set automatic updates.) Security software can detect viruses and protect you from malware, including the malware used by attackers to perform session hijacking.

 

4. Be wary of con artists. Avoid clicking on any link in an email unless you've confirmed it's from a legitimate sender. Session hijackers may send you an email with a link to click. The link may install malware on your device or redirect you to a login page that will log you into a site using a session ID created by the attacker.

 

5. Be mindful of site security. Session hijacking is prevented by safeguards in place at reputable banks, email providers, online merchants, and social media sites. Smart website owners will implement HTTPS across the board, not just on their homepage. 

 

They will also quickly identify and close security flaws. Using dubious online stores or other providers with questionable security can leave you vulnerable to a session hijacking attack.

 

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With so many scams and viruses on the internet, it's difficult to avoid becoming a victim of a session hijacking attack. As a result, it is critical that users are aware of the risks and take every precaution to avoid them.