A cert may refer to any of the following:
1. Short for Computer Emergency Response Team, US-CERT is an arm of the NCSD (National Cyber Security Division) designed to help protect the nation's Internet infrastructure.
2. Cert is used as an abbreviation for certificate, certified, or certification. For instance, "The public key cert of the web server is misconfigured, resulting in an error." Or, "She received her CCNA cert today. Now that she is certified, she is due for a promotion."