[1] From SANS Institute https://www.sans.org/security-resources/glossary-of-terms
[2] From NIST https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.199.pdf
[3] From Information Security Glossary http://www.yourwindow.to/information-security/gl_dataclassification.htm
[4] From Wikipedia https://en.wikipedia.org/wiki/Information_security
[5] Merriam-Webster’s Dictionary definition
[6] From US-CERT https://www.us-cert.gov/government-users/compliance-and-reporting/incident-definition