The protection of information and information systems from unauthorized access, use, disclosure, disruption, modification, or destruction in order to provide confidentiality, integrity, and availability.
Sources:
FIPS 200 under INFORMATION SECURITY from 44 U.S.C., Sec. 3542
CNSSI 4009-2015 from 44 U.S.C., Sec. 3542
NIST SP 1800-10B under Information Security from FIPS 199, 44 U.S.C., Sec. 3542
NIST SP 1800-25B under Information Security from FIPS 199, 44 U.S.C., Sec. 3542
NIST SP 1800-26B under Information Security from FIPS 199, 44 U.S.C., Sec. 3542
NIST SP 1800-27B under Information Security from FIPS 200
NIST SP 1800-27C under Information Security from FIPS 200
NIST SP 800-12 Rev. 1 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-128 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-137 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-160 Vol. 2 Rev. 1 from OMB Circular A-130 (2016)
NIST SP 800-18 Rev. 1 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-30 Rev. 1 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-39 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-60 Vol. 1 Rev. 1 under Information Security from 44 U.S.C., Sec. 3542
NIST SP 800-60 Vol. 2 Rev. 1 under Information Security from 44 U.S.C., Sec. 3542
NISTIR 7621 Rev. 1 under Information Security from 44 U.S.C., Sec. 3542
NISTIR 8170 under Information Security from 44 U.S.C., Sec. 3541

  The term 'information security' means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification, or destruction in order to provide integrity, confidentiality, and availability.
Sources:
NIST SP 800-59 under Information Security from 44 U.S.C., Sec. 3542 (b)(1)

  The protection of information and systems from unauthorized access, use, disclosure, disruption, modification, or destruction in order to provide confidentiality, integrity, and availability.
Sources:
NIST SP 800-128 from 44 U.S.C., Sec. 3552
NIST SP 800-172 from 44 U.S.C., Sec. 3552
NIST SP 800-172A from 44 U.S.C., Sec. 3552
NIST SP 800-37 Rev. 2 from 44 U.S.C., Sec. 3552
NIST SP 800-53 Rev. 5 from OMB Circular A-130 (2016)
NIST SP 800-53A Rev. 5 from OMB Circular A-130 (2016)
NIST SP 800-53B from OMB Circular A-130 (2016)
NIST SP 800-171 Rev. 2 from 44 U.S.C., Sec. 3552

  

Protecting information and information systems from unauthorized access, use, disclosure, disruption, modification, or destruction in order to provide—

(A) integrity, which means guarding against improper information modification or destruction, and includes ensuring information non-repudiation and authenticity;

(B) confidentiality, which means preserving authorized restrictions on access and disclosure, including means for protecting personal privacy and proprietary information; and

(C) availability, which means ensuring timely and reliable access to and use of information.