Session Hijacking – What You Need to Know

how to prevent session hijacking

Hackers use the information saved in cookies, including session IDs, to gain unauthorized access to a computer system. This enables them to perform a variety of attacks, including installing programs and browser toolbars.

Attackers can steal session IDs by monitoring data packets sent between the user’s browser and website server. This is known as session sniffing. During the COVID-19 pandemic, video conferencing apps like Zoom became a popular target for hijacking, which earned the attack the nickname Zoom bombing.

What Is It?

Cybercriminals use Session Hijacking to impersonate an authorized Internet user and carry out actions on a service. This can include stealing money from the victim’s bank account, buying items, committing identity theft, or even encrypting data and demanding ransom for its return.

A criminal must first obtain the user’s session ID to hijack a session. This is usually done by sniffing for it in network traffic. Though most services encrypt login pages to keep passwords safe, hackers can use packet sniffers or proxy tools like Wireshark or OWASP Zed to capture sessions for unencrypted websites.

Once the attacker has a valid session ID, they can use it to perform any action they are authorized on the website, assuming the victim’s online identity. The session ID is a string of numbers and letters stored in temporary session cookies, URLs, or hidden fields on the site.

Attackers can steal a session ID by using malware or directly accessing the victim’s computer. Hackers can also gain access by exploiting software vulnerabilities. For example, an outdated browser or a plugin can expose the computer to attacks. A good defense against these threats includes installing software updates and running a security solution that checks for vulnerability detection. Another option is to implement an IDS and IPS that compares site traffic to a database of attack signatures and blocks it, preventing malicious activity.

How It Works

The user must start a session to log into a website or portal. Once a session is activated, the communication between the two systems will continue until the user decides to stop it.

Cybercriminals are constantly seeking ways to steal a user’s session. They use many methods, such as cross-site scripting (XSS), sniffing, and man-in-the-middle attacks. Attackers who steal a session can perform several tasks, such as injecting malware into a computer, stealing sensitive information, or even draining bank accounts.

During a session hijacking attack, the attacker will try to predict the session ID using available information. Once they can indicate the sequence number, they can intercept packets between the workstation and server to hijack the communication.

To avoid this, use a web application firewall to detect abnormal traffic patterns between your workstation and the server. Another good measure is SSL/TLS encryption on all communications, especially when logging into websites and portals.

XSS is an active type of session hijacking, where the attacker will insert a malicious script into a website’s page. This enables them to access the victim’s browser, sending their session cookie to the attacker’s system. This attack requires access to the victim’s network, often found over unsecured and public WiFi networks.


When you log in to a website or application, it installs a session cookie in your browser. This cookie lets the server know you are logged in and authenticated. Criminals can use this to hijack your session, which allows them to take over your account, steal your personal information, or carry out fraudulent transactions on your behalf.

This attack relies on the attacker already having a known session ID from another site in their possession (for example, via a social media or email account). The criminal then sends the victim a malicious login link that looks authentic but appends the criminal’s session ID. When the victim logs into the site with the fake session ID, the criminal continues the hijack.

The attack can be carried out through various methods, including man-in-the-middle attacks, cross-site scripting, and packet sniffing. It also requires access to a network, which usually implies using an unsecured WiFi hotspot.

Criminals can also target websites and applications that don’t set session cookies, making them more vulnerable to this attack. Reputable banks, online retailers, and webmail providers have safeguards to avoid session hijacking. Avoid clicking on email links, and only use reputable online shopping sites.


Whenever an authorized user logs in to an online service, the server sets a session cookie that keeps them logged in and authenticated. If an attacker intercepts a session cookie, they can masquerade as the authorized user and perform unauthorized activities on the website, such as making transactions or changing account information.

The most common method of attack is through cross-site scripting, which allows attackers to inject JavaScript code into web pages and trick browsers into executing the code when they load a compromised page. This attack can be prevented using secure HTTPS connections and installing reputable security plugins on WordPress websites.

Malware attacks are also a standard method of session hijacking. Once an attacker has installed malware on a victim’s computer, it can scan the victim’s network for web traffic, including session cookies. It can then report back the cookie values or access them directly.

Users can limit risk using reputable banks, online shopping, and email services to avoid session hijacking. Using a VPN can help as well. A VPN will encrypt all your data so that even if a criminal intercepts packets, they won’t be able to read any information on the unsecured connection. Lastly, strong passwords and two-factor authentication (2FA) can prevent hackers from accessing accounts even if they can steal login credentials.

Gabriel Montgomery

Gabriel Montgomery

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