Website Security Basics Every Developer Must Know
A hacked website loses visitors, rankings and trust. Most attacks use well-known weaknesses that are easy to prevent if you build with security in mind.
Protect your data
Use https everywhere. Never trust user input: validate it and use prepared statements to stop SQL injection. Escape output to prevent cross-site scripting.
Protect your accounts
Hash passwords with a strong algorithm such as bcrypt, never store them in plain text, and offer two-factor login. Keep your server, CMS and plugins updated.
Prepare for problems
Take regular backups and test restoring them. Limit who has admin access and monitor your logs. Security is a habit, not a one-time task.
The most common attacks
SQL injection happens when an attacker types database commands into a form and your code runs them. Cross-site scripting, called XSS, happens when a page displays untrusted text that contains a hidden script, which then runs in other visitors’ browsers. Cross-site request forgery tricks a logged-in user into sending an action they did not intend. Brute-force attacks try thousands of passwords until one works. Knowing these names helps you search for the right defence.
Validate and sanitise every input
Treat all data from users, URLs, cookies and files as unsafe. Check the type, length and format on the server, not only in the browser, because browser checks are easy to bypass. Use prepared statements for databases and escape text before showing it on a page. Limit file uploads to allowed types and sizes, and store them outside the public folder when possible.
Passwords and login
Never save passwords as plain text. Use a slow hashing algorithm such as bcrypt or Argon2 with a unique salt. Require a reasonable minimum length, block the most common passwords and limit login attempts to slow brute-force attacks. Offer two-factor authentication for admin accounts. Reset links should expire quickly and work only once.
Use https and secure headers
An SSL certificate encrypts data between the visitor and your server. Most hosts offer it free. Redirect all http traffic to https and set the secure flag on cookies. Add security headers such as Content-Security-Policy, X-Frame-Options and Strict-Transport-Security. They tell the browser to block many kinds of attacks, and online scanners can check your setup in minutes.
Keep everything updated
Many hacked websites run old plugins or old versions of a CMS such as WordPress. Update your software, themes and libraries regularly, and delete the ones you do not use. Subscribe to security notices for the tools you depend on. Use only trusted plugins, because a single weak plugin can expose the whole site.
Backups and monitoring
Keep automatic backups in a different place from your server and test that you can restore them. Watch your logs for strange activity such as many failed logins. Use uptime monitoring so you know quickly if the site goes down. If you are attacked, change all passwords, restore a clean backup, patch the weakness and inform affected users.
A simple security checklist
Use https, validate input, hash passwords, enable two-factor login, update software, back up daily and limit admin access. Review the list every month. Building these habits from your first project means you will never have to learn security the hard way after a site has been damaged.