What is CSRF attack and how does it work?

CSRF (Cross-Site Request Forgery) is a type of web attack where attackers trick users into performing unintended actions on authenticated websites.

How It Works

1. User Login: User logs into the target website (e.g., banking site), server creates session and returns Cookie
2. Cookie Storage: Browser stores the target website's Cookie locally
3. Visit Malicious Site: User visits a malicious website controlled by the attacker
4. Send Request: Malicious site contains requests to the target website (e.g., form submission, AJAX request)
5. Auto-send Cookie: Browser automatically sends the target website's Cookie
6. Execute Action: Server validates the Cookie and executes the requested action

Attack Conditions

• User is logged into the target website
• Target website uses Cookie for authentication
• Browser automatically sends Cookies
• Target website lacks other protection mechanisms

Common Attack Scenarios

• Bank transfers
• Password changes
• Data deletion
• Sending emails
• Adding admin accounts

Defense Measures

1. CSRF Token: Add random Token to forms, server validates it
2. SameSite Cookie: Set Cookie's SameSite attribute
3. Verify Referer/Origin: Check request source
4. Double Submit Cookie: Include Token in both Cookie and request parameters
5. Custom Header: Use custom Header for validation

Difference from XSS

• CSRF: Uses user's identity, doesn't require script injection
• XSS: Injects malicious scripts, can steal Cookies or execute arbitrary operations

CSRF attacks exploit the browser's automatic Cookie sending mechanism and are a significant threat to web application security.