Building a web application is only half the battle; securing it is the other half. Every day, thousands of web applications are compromised due to easily preventable vulnerabilities. As a developer, it is your responsibility to understand these attacks so you can write secure code from day one. Let's break down the Top 5 web attacks and how to mitigate them.

1 SQL Injection (SQLi)

SQL Injection occurs when an attacker can insert malicious SQL statements into a database query via user input. If an application takes input from a login form and blindly concatenates it into a database query, an attacker could input ' OR '1'='1 to bypass authentication entirely.

Prevention: Always use Parameterized Queries (Prepared Statements) or an ORM like Hibernate or Prisma. Never concatenate raw user input into SQL strings.
2 Cross-Site Scripting (XSS)

XSS happens when an application includes untrusted data in a web page without proper validation or escaping. This allows attackers to execute malicious JavaScript in the victim's browser, which can be used to steal session cookies, log keystrokes, or redirect the user to a malicious site.

Prevention: Sanitize and encode all user input before rendering it in the browser. Modern frameworks like React and Angular automatically escape string variables by default, providing strong built-in protection against XSS.
3 Cross-Site Request Forgery (CSRF)

CSRF is an attack that forces an end user to execute unwanted actions on a web application in which they are currently authenticated. Because the browser automatically sends session cookies with requests, an attacker can embed a malicious link on a third-party site. If the user clicks it, a state-changing request (like transferring funds) is executed on their behalf.

Prevention: Use Anti-CSRF tokens for any state-changing requests, and configure cookies with the SameSite=Strict or Lax attribute.
4 Distributed Denial of Service (DDoS)

A DDoS attack attempts to disrupt the normal traffic of a targeted server by overwhelming it with a flood of Internet traffic from multiple compromised computer systems. The goal is to exhaust the server's resources so legitimate users cannot access the site.

Prevention: Use rate-limiting in your backend API, implement CDNs (like Cloudflare) for traffic filtering, and employ web application firewalls (WAF).
5 Man-in-the-Middle (MitM)

In a MitM attack, the attacker secretly intercepts and relays communications between two parties who believe they are directly communicating with each other. This often occurs on insecure public Wi-Fi networks, allowing attackers to steal login credentials or personal data being transmitted.

Prevention: Enforce HTTPS everywhere using TLS certificates, and implement HTTP Strict Transport Security (HSTS) headers.
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Security is a Mindset
Never trust user input. By adopting a "defense in depth" strategy and understanding these top vulnerabilities, you'll be well on your way to building robust and secure web applications.