mod_security

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Overview

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 in the panel.

Enabling Mod_security

  1. Navigate to the (Panel > ‘Domains’ > ‘Manage Domains’) page.
  2. Under your domain, click the ‘DNS’ link.
    The ‘Manage Domains’ page appears:
    Mod security enable.fw.png
    • Under the ‘Web Options’ section, the checkbox titled ‘Extra Web Security?’ is enabled by default.
  3. If you wish to disable Mod_security, then 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 will be blocked by this option, but there are no guarantees that all attacks will be prevented. With Extra Web Security enabled, DreamHost will proactively ensure that the most commonly known attacks are prevented.

Mod_Security related log entries

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.

See also