Session Hijacking: What is It, Its Types, and How it Works?

Quick Summary: While the internet is the most useful thing today, it is not free of problems and challenges. There are various cyber security threats that pose real challenges for internet users. Session hijacking is one of those dangers that enable an attacker to obtain control over a user’s web session and exploit it for various malicious purposes. This article sheds light on this threat, helping you understand every aspect in detail, and puts down some ways for session hijacking prevention. Read for your enlightenment.

Imagine a scenario when you log in to a website and all of a sudden, an attacker takes control of your session. It is a kind of malicious activity wherein an attacker snatches the control of a user’s browsing session. The attacker misuses the access to the session token by committing fraud and crimes.

According to a report, there are about 2.7 billion worth of assets of Fortune 1000 employees exposed to the dark web. Mostly the reason for this vast data breach was session cookies. This shows the dangers of a session hijacking attack and the financial implications of this.

These attacks can occur due to many reasons primarily vulnerabilities in software and a lack of solid security mechanisms. Attackers can perform session hijacking with or without installing malware and detecting these threats can be challenging.

It is essential to follow the right steps to prevent this malicious attack and safeguard your data. Plus, you need a robust vulnerability scanning tool to identify potential weaknesses to mitigate this type of security risk. In this blog, we are going to discuss session hijacking in detail and the ways to prevent it. Let’s dive into the blog for more details.

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What is Session Hijacking and Its Implications?

In the simplest way, it is an act of obtaining control of a user’s web session maliciously. A session, or more precisely a web session, denotes the amount of time a user logs in to a website or web app to log out. It is the duration of interaction between two endpoints. Both endpoints use a unique session token that ensures a consistent and secure interaction.

A session hijack attack occurs when an attacker successfully gets unwarranted access to a website or web app masquerading as a genuine user by manipulating or stealing a session token. Attackers use various techniques like brute force, cross-site scripting, session fixation, and more to hijack a session. Session hijacking is alternately known as TCP session hijacking and cookie hijacking.

It poses a serious security threat when an attacker takes control of a legitimate user’s internet session. The user’s sensitive information is at risk because the session hijacking can occur when banking or shopping online. The session hijacker masquerades as a user and steals passwords and personal information by taking control of the browsing session.

Some security threats that occur due to session hijacking:

• Identity Theft: A session hijacker can steal and misuse a user’s personal information. The hijacker can commit crimes, take loans, and cause all other misdeeds masquerading as the victim.
• Frauds: Financial fraud is another serious threat that arises due to session hijacking. Once obtaining access to a website or web app masquerading as a legitimate user, the hijacker can do unauthorized financial transactions, transfer money, or shop online.
• Communication Breach: In this highly digital world, confidential communications like secret business meetings are conducted online. A session hijacker can take control of any user’s session and leak confidential information.
• Denial-of-Service (DoS) Attack: A session hijacker can also launch a DoS attack that causes disruption of service or crash.

Session Hijacking vs. Session Spoofing: What’s the Difference

Session hijacking and session spoofing are often confused because both involve unauthorized access to a system. However, they work in different ways. Session hijacking takes over an existing authenticated session, while session spoofing involves impersonating a user to establish a new session without using the victim's active session.

How Does Session Hijacking Work?

Now that you have enough information about what session hijacking is and its implications, it’s time to discuss the process of hijacking session. Understanding how session hijacking works can help you make the right decisions for web application security testing. Let’s start by knowing the entire web session mechanism.

• Let’s assume that a user wants to access a resource on a web app.
• First, the user will sign in/login to the web with their credentials.
• As soon as the server verifies the credentials, the user is logged in.
• The server provides a response with a unique session ID.
• After the successful login activity, the session started.
• The session ID enables the application to track the user’s activity.
• The browser sends a session termination request when logging out.
• The session is terminated by the server.

Whenever a user logs in successfully, the target website or web app installs a temporary session cookie to the user’s browser. The cookie tracks the user’s activities and has authentication information to help the user stay logged in through an active session. The cookie remains until the user logs out.

One of the ways to hijack a session is by stealing the session cookie installed on a user’s browser. After stealing the cookie, the hijacker accesses the session ID in the cookie and then takes over control of the session. The hacker can gain access to a session without detection.

The hijacker will misuse the ongoing session to commit crimes, identify theft, and steal financial information. It can include purchasing items, transferring money from the bank account, and more. Hijackers often commit session attacks on busy networks where there are a large number of active users because it is difficult to detect them.

Preventing session hijacking is crucial to safeguard sensitive data and your reputation. The best method to combat threats like session hijacking is conducting an advanced penetration testing. It performs simulated attacks on running applications to discover vulnerabilities. It helps to detect security weaknesses most reliably and with minimum false positives. Developers can fix these vulnerabilities before they get exploited by a hacker.

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Understanding the Various Types of Session Hijacking

There are different forms of session hijacking and each of them occurs for various reasons. But from a broader perspective, session hijacking can be: active or passive. In active hijacking, the attacker steals or gains access to the session token that enables the attacker to take control of the session. In passive hijacking, the attacker collects information surreptitiously and doesn’t take over the session immediately. Let’s check the types of session hijacking.

Brute Force

In a brute force session hijacking attack, an attacker repeatedly guesses valid session IDs until one matches an active user session. This method is more likely to succeed when applications generate weak or predictable session tokens. Using long, randomly generated session identifiers makes these attacks significantly harder to execute.

Cross-Site Scripting

Cross-Site Scripting (XSS) enables attackers to inject malicious JavaScript into a vulnerable web application. When a user visits the compromised page, the script can steal session cookies or authentication tokens and send them to the attacker. This allows the attacker to impersonate the user without knowing their login credentials.

Session Fixation

A session fixation attack occurs when an attacker tricks a user into logging in with a session ID that the attacker already knows. If the application does not generate a new session ID after successful authentication, the attacker can reuse that session identifier to access the authenticated account.

Session Sidejacking (Session Sniffing)

Session sidejacking involves intercepting network traffic to capture a user's session cookie or token. Attackers often attempt this on unsecured or poorly protected networks. Once they obtain the session token, they can take over the active session and perform actions as the legitimate user.

Malware Attack

Malware-based session hijacking relies on malicious software installed on a victim's device. The malware can steal browser cookies, authentication tokens, or saved session data without the user's knowledge. Attackers then use this information to gain unauthorized access to web applications, even if multi-factor authentication was required during login.

What are the Examples of Session Hijacking Attack?

There are a lot of real-world session hijacking examples where attackers took over user sessions and misused them. The following are some popular examples of such attacks.

Zoom

During the Covid-19 pandemic video-conferencing applications like Zoom became a big hit. While it facilitated users to meet virtually and utilized it for work, get-togethers, and schoolwork, Zoombombing became a huge concern for all stockholders. Zoombombing was an unwanted intrusion into video conference calls to spread obscene or disturbing materials. Hackers and internet-trolls leveraged session vulnerabilities in Zoom to join private calls without permission causing Zoombombing.

Slack

A security researcher identified a session-related vulnerability in Slack in 2017. Attackers could exploit
this vulnerability to compel users for fake session redirects that allowed attackers to access their session cookies. As a result, the attacker could gain access to all kinds of data shared within Slack.

GitLab

A security expert discovered a vulnerability in GitLab in 2017 that led to users’ session tokens appearing in the URL. Plus, further investigation also revealed that GitLab used session tokens that didn’t expire. Consequently, attackers could use such tokens to gain unauthorized access to users’ accounts.

How to Prevent Session Hijacking?

There are many ways to prevent session hijacking as given below.

• Always update software: Updating software is a solid method to prevent session hijack attacks. Get the latest security patches.
• Use a VPN: The use of a VPN prevents cyber criminals from intercepting web traffic which can help to prevent session hijacking in case of unsecured networks.
• Use multi-factor authentication: It is also a robust method to protect your session from hacking attacks. Using strong passwords is another important method to secure your session.
• Scan regularly for vulnerabilities: Scanning applications for vulnerabilities at regular intervals helps to identify weak spots to fix them and mitigate security risks. You must choose the best web application security assessment tool for this.

ZeroThreat for Detecting and Preventing Session Hijacking Risks

Session hijacking often exploits weaknesses in authentication flows, session management, and access controls. ZeroThreat helps identify these risks through AI-powered, context-aware security testing that validates real attack paths before attackers can exploit them.

• Tests Authentication and Session Flows: ZeroThreat performs authenticated security testing to analyze login workflows, session handling, user roles, and authorization logic, helping uncover weaknesses that could enable session hijacking.
• Detects Session Management Vulnerabilities: The platform identifies security issues related to insecure session tokens, improper session validation, broken access controls, and authentication flaws that increase the risk of account takeover.
• Validates Real Attack Paths: Instead of reporting theoretical issues, ZeroThreat safely validates exploitability using controlled techniques. This helps security teams prioritize session-related vulnerabilities that pose genuine business risk.
• Safely Tests Production Environments: With production-safe security testing, ZeroThreat validates live applications using non-destructive techniques, controlled payload execution, and execution safeguards without disrupting users or business operations.
• Continuously Analyzes Security Posture: Continuous security testing and automated revalidation help detect newly introduced session management issues, configuration drift, and authentication risks as applications evolve.
• Delivers Actionable Remediation Guidance: Every validated finding includes proof of exploitability and AI-powered remediation guidance, enabling development and security teams to resolve session security weaknesses faster.

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Final Words

With billions of people using the internet every day for online shopping, social networking, banking transactions, and more, security threats have become a bitter truth. Session hijacking has become one of the biggest threats for online users as it enables attackers to seize their web sessions while masquerading as valid users. It exposes their financial and personal details without detection and prevention.

You need the best security testing tools like ZeroThreat to identify and mitigate such security risks. ZeroThreat is an AI-powered automated pentesting tool that helps to prevent session hijacking with its cutting-edge scanning features. It can detect vulnerabilities most accurately with zero false positives and offers faster scanning speed.

ZeroThreat offers an AI-driven crawler that can scan web applications meticulously to discover potential security weaknesses. It provides priority-based reports to expedite your AppSec process. Try it for free and enhance the security of your web applications with accurate vulnerability scanning results.