mod_security is a Web Application Firewall (WAF) that filters and blocks known malicious HTTP requests. Blocked HTTP requests include many, but not all forms of Brute Force, Cross-Site Scripting (XSS), Remote File Inclusion (RFI) , Remote Execution, and SQL injection (SQLi) attacks. DreamHost enables mod_security by default, with the Extra Web Security option that you can enable in the panel.
- Navigate to the (Panel > ‘Domains’ > ‘Manage Domains’) page.
- To the right of your domain, click the Edit button.
- Under the ‘Web Options’ section, the checkbox titled ‘Extra Web Security?’ is enabled by default.
- If you wish to disable mod_security, un-check this box and save the change(s).
The Extra Web Security option enables the use of a special security module for your website. Many common attacks that can compromise your website are blocked by this option, but there are no guarantees that all attacks will be prevented. With Extra Web Security enabled, DreamHost proactively ensures that the most commonly known attacks are prevented.
DreamHost uses the HTTP response code 418. If a user sees 418 response codes in their access.log files, it means that the request was blocked by mod_security.
Further details related to the block are often in the corresponding date stamped error.log entry. If you are having trouble deciphering why you are getting a 418 error in your log files, please don’t hesitate to contact support at (DreamHost Panel > 'Support' > 'Contact Support').
DreamHost mod_security rules
While a majority of DreamHost’s mod_security rule set is custom created as threats emerge, the base of DreamHost’s mod_security rule set comes from the OWASP mod_security Core Rules Set.
An important note about modifying .htaccess mod_security rules
Disabling and modifying of mod_security rules via .htaccess is not supported at this time.