Cookie hijacking occurs when an attacker intercepts or steals the small data files that websites store in your browser. These cookies contain session tokens, which act like temporary passwords that keep you logged into your accounts. By stealing them, the attacker can masquerade as you on any site where you're currently logged in.
Attackers use several methods to steal cookies:
- Man-in-the-middle attacks: Intercepting unencrypted traffic on public WiFi networks
- Cross-site scripting (XSS): Injecting malicious code into websites to extract cookies from visitors
- Malware: Installing software on your device that reads browser storage
- Session fixation: Forcing your browser to use a cookie the attacker controls
Once stolen, attackers gain immediate access to your email, banking, social media, or shopping accounts. They bypass two-factor authentication on the site itself because the cookie confirms your login is already valid. This is particularly dangerous because you may never know the breach happened.
To protect yourself, ensure websites use HTTPS encryption (check the padlock icon), avoid logging in on public WiFi, and keep your browser updated. Websites should use HttpOnly and Secure cookie flags to prevent JavaScript theft and force encrypted transmission. Regular password changes and checking account activity logs help catch hijacking early.