WordPress Security Hardening Checklist — What We Do for Every Client Site

WordPress powers over 40% of the web. That also makes it the most common target. We've cleaned up many hacked WordPress sites — malware injected into core files, redirects to phishing pages, backdoors hidden in plugins. This post shares the security checklist we apply to every client website.

This isn't theory. Every item in this checklist originated from a real incident we encountered and resolved.

1. File Permissions

Incorrect file permissions are the most common reason malware can write files to the server. WordPress standards:

• Directories: 755 (owner read/write/execute, group and others read/execute only)
• Files: 644 (owner read/write, group and others read only)
• wp-config.php: 600 or 640 — this file contains database credentials, nobody besides the owner needs to read it

Many shared hosting providers set permissions to 777 for the uploads directory — anyone on the server can write files there. This is inviting hackers in.

# Fix permissions for entire WordPress installation
find /path/to/wordpress -type d -exec chmod 755 {} \;
find /path/to/wordpress -type f -exec chmod 644 {} \;
chmod 600 /path/to/wordpress/wp-config.php

2. Login Protection

Brute force is the simplest attack method — bots try thousands of username/password combinations. Countermeasures:

• Limit failed login attempts. Limit Login Attempts Reloaded plugin — free, effective. After 3 failures, lock IP for 15 minutes. After 3 lockouts, lock for 24 hours.
• Don't use "admin" as username. Bots always try "admin" first. Create hard-to-guess usernames.
• Change login URL. Default is /wp-login.php and /wp-admin/. Change to a custom URL. Not bulletproof security — but eliminates 90% of bots.
• Two-factor authentication. For admin accounts, 2FA should be mandatory. WP 2FA plugin works well.

3. Disable XML-RPC

XML-RPC (/xmlrpc.php) is WordPress's legacy API — allows posting from external applications. Most sites don't need it, but it's open by default. The problem: XML-RPC allows trying multiple passwords in one request (system.multicall) — bypassing login rate limits.

# In .htaccess (Apache)
<Files xmlrpc.php>
  Require all denied
</Files>

Or in Nginx:

location = /xmlrpc.php {
  deny all;
  return 403;
}

If you need XML-RPC (e.g., for Jetpack), whitelist specific IPs instead of opening it to everyone.

4. HTTP Security Headers

Headers don't prevent server-side malware — but they protect users from client-side attacks (XSS, clickjacking, MIME sniffing):

# Add to .htaccess or nginx config
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()

Content-Security-Policy (CSP) is the most effective but also most complex — easy to break things if misconfigured. We add CSP gradually, testing thoroughly before enforcing.

5. Disable File Editing in Admin

WordPress by default allows editing plugin and theme files from the admin panel. If an admin account is compromised, hackers can inject malware directly from the web interface.

// Add to wp-config.php
define('DISALLOW_FILE_EDIT', true);
define('DISALLOW_FILE_MODS', true); // Also disables plugin/theme install from admin

DISALLOW_FILE_MODS also disables plugin/theme updates from admin — you'll need to update via WP-CLI or SFTP. This is a safe trade-off: less convenient, but significantly more secure.

6. Database Security

• Change table prefix. Default is wp_. Change to a random prefix to make SQL injection attacks harder (not impossible, but adds a layer).
• Dedicated database user for WordPress. Don't use root. The user should only have SELECT, INSERT, UPDATE, DELETE permissions on the WordPress database — no DROP, ALTER, GRANT.
• Remove unused tables. Old plugins leave orphan tables in the database. Clean up periodically.

7. Plugin and Theme Hygiene

Outdated plugins and themes are the most common attack vector. Rules:

• Delete unused plugins — don't just deactivate. Inactive plugins can still be exploited if they have vulnerabilities.
• Delete unused default themes. Keep the active theme + one default theme (Twenty Twenty-Four) for fallback.
• Never use nulled/cracked plugins. 100% contain malware. No exceptions.
• Vet plugins before installing. Check last update date, number of active installs, rating. Plugins not updated in >1 year = risk.
• Auto-update minor versions. WordPress minor updates (5.9.1 → 5.9.2) are mainly security patches. Enable auto-updates.

8. Backup — The Last Line of Defense

Every security measure can be bypassed. Backup is the only thing that lets you recover when everything else fails.

• Daily backups — both files and database
• Store offsite — not just on the same server. If the server is compromised, backups on it are too.
• Keep 30 days — sometimes malware is only discovered weeks later. You need clean backups from before infection.
• Test restores — backups are meaningless if they can't be restored. Test at least quarterly.

9. Speed Optimization — Indirect Security

A slow website is often a sign of security issues — malware injecting code, abnormal database queries, or simply weak hosting that can't run security plugins.

• Page caching — reduces PHP processing load. WP Super Cache or W3 Total Cache.
• Object caching — Redis or Memcached for database query caching.
• CDN — Cloudflare free tier reduces server load and adds basic WAF.
• Image optimization — uncompressed images account for 50-80% of page weight. WebP conversion + lazy loading.
• PHP version — PHP 8.2+ is significantly faster than 7.4. Upgrading PHP is the quickest optimization.

When the Site Is Already Hacked

If the site is already infected with malware, the checklist above isn't enough. Recovery process:

1. Isolate — take the site offline or into maintenance mode immediately. Prevent malware from spreading and protect users.
2. Scan entire filesystem — find abnormal files, recently created files, obfuscated code. wp-cli has wp core verify-checksums to compare core files against originals.
3. Reinstall WordPress core — wp core download --force. Keep wp-content/ and database.
4. Check every plugin and theme — compare against originals from wordpress.org. Any modified file = suspicious.
5. Check database — look for JavaScript/iframe injection in posts, options, user metadata.
6. Change all credentials — admin passwords, database password, SFTP, hosting panel.
7. Apply security checklist — all items above.
8. Resubmit to Google Search Console — request removal of "This site may be hacked" warning.

The entire process takes 2-4 hours for a simple site, 1-2 days for complex ones. But more important is preventing reinfection — that's why the security checklist must be applied immediately after cleanup.

Conclusion

WordPress security isn't hard — but it requires discipline. Most sites get hacked not because hackers are skilled, but because site owners forgot to update plugins, used weak passwords, or installed cracked themes.

This checklist isn't invulnerable. But it eliminates 95% of common attack vectors — and that's the difference between a secure site and one that will be hacked within the next 6 months.