Information Security: Advanced Persistent Threat (APT)

"A sustained, human-intensive attack that leverages the full range of computer intrusion techniques." (Manish Agrawal, "Information Security and IT Risk Management", 2014)

"A group or entity that has the capability and intent to persistently target a specific organization. They typically have the backing of an organization with almost unlimited resources, such as a government." (Darril Gibson, "Effective Help Desk Specialist Skills", 2014)

"A network attack in which an unauthorized person gains access to a network and stays there undetected for a long period of time. The intention of an APT attack is to steal data rather than to cause damage to the network or organization. APT attacks target organizations in sectors with high-value information, such as national defense, manufacturing, and the financial industry. APTs differ from other types of attack in their careful target selection and persistent, often stealthy, intrusion efforts over extended periods." (William Stallings, "Effective Cybersecurity: A Guide to Using Best Practices and Standards", 2018)

"Sophisticated attacks that are carefully crafted by hostile governments or organizations, usually for political vengeance or financial gain. They often combine the most advanced malware, spear-phishing, and intrusion techniques available." (Mark Rhodes-Ousley, "Information Security: The Complete Reference, Second Edition" 2nd Ed., 2013)

"An adversary that possesses sophisticated levels of expertise and significant resources which allow it to create opportunities to achieve its objectives using multiple attack vectors." (NIST SP800-61)

"An adversary with sophisticated levels of expertise and significant resources, allowing it through the use of multiple different attack vectors (e.g., cyber, physical, and deception) to generate opportunities to achieve its objectives, which are typically to establish and extend footholds within the information technology infrastructure of organizations for purposes of continually exfiltrating information and/or to undermine or impede critical aspects of a mission, program, or organization, or place itself in a position to do so in the future; moreover, the advanced persistent threat pursues its objectives repeatedly over an extended period of time, adapting to a defender’s efforts to resist it, and with determination to maintain the level of interaction needed to execute its objectives." (CNSSI 4009-2015)