The purpose of an advanced persistent threat (APT) in cyberattacks is to gain unauthorized access to a network over an extended period, often targeting sensitive data or critical infrastructure. APTs are characterized by their stealthy nature and determination; attackers use sophisticated methods to bypass security measures, maintaining a presence in the system to achieve long-term goals. These types of threats pose severe risks to organizations, leading to potential data breaches, financial loss, and reputational damage.