Google maintains the Google Safe Browsing databases, and an API that allows us to check URLs against Google’s lists of malware and phishing sites.

The gsbdaily filter runs once every 24 hours and performs a more exhaustive search than the gsb filter. It checks the URL that is being monitored, every link from that URL, and then every link from every one of those secondary URLs. In other words, it checks three levels of pages and files.

It’s a fairly costly exmination in terms of the number of requests it has to make, which can be in the thousands for some large sites, so we perform it only once a day.

Note: The gsb filter does a less thorough, but much faster, analysis each time the filter runs.