This List includes cybersecurity companies located in the Greater Bay Area, which is defined as Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano and Sonoma counties. Information was obtained from company representatives. In case of ties, companywide employees was used as secondary ranking criteria. Malwarebytes (No. 10 on last year’s List) declined to participate. ThreatMetrix (No. 23 on last year’s List) was acquired by RELX in 2018. The following companies ranked last year did not respond to requests for information: A10 Networks (No. 9), ForeScout Technologies Inc. (No. 11), Lookout (No. 13), Centrify Corp. (No. 14), Tanium Inc. (No. 15), Illumio (No. 20), Sift Science (No. 21), Accellion Inc. (No. 24) and Exabeam (No. 25).