This document answers frequently asked questions about the Google Safe Browsing Service in Mozilla Firefox version 3
How does the Safe Browsing feature in Firefox 3 work?
The Safe Browsing feature in Firefox 3 is designed to protect your machine and your privacy, while conserving transmission bandwidth by sending very small amounts of data to and from your machine. To provide the Safe Browsing feature, Google downloads to your browser a list of information about sites that may contain malicious software or engage in phishing. The list does not include the full URL of each suspicious site. Instead, each URL is hashed (obscured so it can't be read) and then broken into portions. Only a portion of each hashed URL is included on the list on your browser.
As you browse the web, your browser creates hashed versions of URLs that you visit, and checks them against the list. If a site that you visit appears to match a hashed URL fragment on the list, your browser will contact Google's servers to request the full list ? not just portions -- of the hashed URLs that are believed to be risky. Your machine can then determine if you are visiting a risky site, and warn you about it. When your machine contacts Google to get more information about a specific hashed URL fragment, or to update the list, we receive standard log information including your IP address and possibly a cookie. This information does not personally identify you, and is retained only for a period of weeks. Any information that we receive through this process is protected under the standard terms of the Google Privacy Policy.