What is Session Hijacking?

Session Hijacking is a type of attack that involves exploiting the web session control mechanism. Attackers use this method to take over someone's internet session by stealing the session token. Session hijacking is also known as cookie hijacking or cookie side-jacking.

In a session hijacking attack, the attacker deceives a website into thinking they are the legitimate user. This attack can severely affect application security by allowing unauthorized access to protected accounts.

Common Types of Session Hijacking

• Cross-site Scripting (XSS): Attackers exploit vulnerabilities by injecting scripts into web pages. In this way, they can access your session key and take over your session. 
• Session Side-Jacking (Session Sniffing): The attacker gains unauthorized access to a user's network traffic, usually through unsecured Wi-Fi or man-in-the-middle attacks. The attacker monitors the user's network traffic to find active sessions and obtain session cookies to take over the session, potentially leading to unauthorized access to sensitive information.
• Man-in-the-Browser Attack: A Trojan is used to modify transaction information and create additional transactions without the victim's knowledge. The requests are initiated from the victim's computer, making it difficult for the web service to detect the fraud.
• Predictable Sessions Token ID: Many web servers generate session IDs using a custom algorithm or predefined pattern. Attackers may capture several IDs and analyze the pattern to predict a valid session token if it is predictable.

How does Session Hijacking Work

• Session hijacking occurs when an unauthorized user gains access to a user's session ID. This access is usually achieved by stealing a user's session cookie, also known as cookie hijacking, or by persuading the user to click on a malicious link that contains a predicted session ID. 
• After obtaining the session ID, the attacker can take control of the session by using the legitimate user's session ID in their browser, tricking the service into thinking that the attacker is the legitimate user engaging in that same session. 
• With this access, the attacker can impersonate the legitimate user and access any information or perform any action that the user is authorized to do. 
• Alternatively, in the case of single sign-on (SSO) users, the attacker can use this method to gain unauthorized access to any number of applications, severely compromising application security across the board.

Session Hijacking Examples

• During an investigation, cybersecurity firm Mandiant discovered that an organization fell victim to a targeted attack that exploited the Heartbleed OpenSSL vulnerability. The attackers specifically targeted an SSL VPN concentrator to steal active user session tokens, which allowed them to bypass the organization's multifactor authentication. As a result, the VPN was convinced that the attackers were authorized users, giving them access to sensitive information. This marks the first publicly known real-world attack that leveraged Heartbleed for session hijacking.
• Between September 28, 2023, and October 17, 2023, Okta suffered a data breach that impacted over 130 of its customers. During the breach, unauthorized access was gained to files within Okta's customer support system. The files compromised included HTTP Archive (HAR) files that contained session tokens. As a result, five of Okta's customers had their sessions hijacked, with companies such as 1Password, BeyondTrust, and Cloudflare reporting suspicious activity and unauthorized login attempts to their Okta administrator accounts. The attackers were able to obtain credentials for a support service account by accessing an Okta employee's personal Google account, which was accessed on an Okta-managed laptop.

Impacts of Successful Session Hijacking

Session hijacking poses significant risks that should not be ignored. Some of the potential dangers include:

• Identity Theft: Attackers can gain unauthorized access to sensitive personal information saved in accounts, resulting in identity theft beyond the hacked website or application.
• Financial Loss: With session hijacking, attackers can carry out financial transactions on behalf of the user, such as transferring money from a bank account or making purchases with saved payment information.
• Malware Infection: If a hacker can steal a user's session ID, they may also be able to infect the user's computer with malware, giving them control of the target's computer and the ability to steal their data.
• Denial-of-Service (DoS) Attacks: A hacker who gains control of a user's session could launch a DoS attack against the website or server, disrupting service or causing a crash.
• Gaining Access to Systems with SSO: Enabling single sign-on (SSO) can increase the risk of unauthorized access to additional systems, leading to session hijacking attacks. This is particularly important for organizations that use SSO for employees. Even systems with stronger authentication protocols and less predictable session cookies, such as those that store financial or customer information, may only be as secure as the weakest link in the entire system. It's crucial to ensure SSO is implemented securely to reduce the potential risks.

Mitigation Strategies for Session Hijacking

To defend against session hijacking attacks, individuals and organizations can implement various mitigation strategies:

• Use SSL:  SSL (Secure Sockets Layer) provides a secure protocol for communication over the Internet. By encrypting the communication between a user's browser and your website, SSL can help prevent session hijacking, which makes it difficult for attackers to intercept and steal session cookies.
• Implement Strong Password Policies: Strong password policies can make it harder for malicious actors to access other accounts and systems with a single attained password. Using different, strong, long, and unique passwords prevents hackers from finding passwords by guessing or using a captured password to gain access to other accounts.
• Monitor Activities: Monitoring activities on your site, such as failed login attempts, unauthorized access attempts, or unusual user behavior, can help detect hijacked user accounts early and prevent them from causing damage.
• Enable MFA: Enabling MFA (Multi-Factor Authentication) adds an extra layer of security to user accounts. By requiring users to provide a second factor, such as a code sent to their mobile device, in addition to their password, MFA can prevent attackers from accessing user accounts even if they have managed to steal login data from session cookies.
• Use Firewall: Using a firewall program can block malicious traffic and filter out malicious requests that attempt to exploit vulnerabilities in the session to prevent session hijacking attacks.

Related Terms

• Spoofing
• MFA
• SSO

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