"Search engines on the Internet today are powerful software tools that crawl and categorize massive amounts of information. Search engines like Google, Bing, etc., continue to increase the speed at which they can 'crawl' the Internet and the types of data they can consume and categorize. Today these search engines consume and create metadata on web pages, various document files, videos, and images among others. [...] There are many resources available to assist in advanced search engine use; just Google it. Most of the search commands listed here will work across various search engines; however, if one does not work, there may be a slight syntax difference required by that search engine. Many of the commands can be combined together to maximize your searching potential."
Industrial Control Systems Cybersecurity Emergency Response Team (ICS-CERT): http://www.ics-cert.us-cert.gov/