Attack - Attempt to gain unauthorized access to an information system's services, resources, or information, or the attempt to compromise an information system's integrity, availability, or confidentiality.
NIST SP 800-28v2
NIST SP 800-63v1.0.2
NIST SP 800-82 Final Draft
Attack - An attempt to gain unauthorized access to system services, resources, or information, or an attempt to compromise system integrity, availability, or confidentiality.[National Information Assurance (IA) Glossary, CNSS Instruction no. 4009, revised June 2006.]