APT stands for Advanced Persistent Threat. An APT attack is a sophisticated and targeted cyberattack where an unauthorized user gains access to a network and remains undetected for an extended period. The term "persistent" indicates that the attacker maintains a long-term presence within the targeted network to achieve specific objectives.

Key characteristics of APT attacks include:

1. Advanced Techniques: APT attackers often employ advanced and sophisticated methods to breach security measures. This may involve the use of zero-day exploits (vulnerabilities that are unknown to the software vendor or the public), custom malware, or other advanced tactics.

2. Persistence: APT attackers aim to remain undetected for a prolonged period to achieve their goals, which could include stealing sensitive information, conducting espionage, or disrupting operations.

3. Targeted: APT attacks are typically targeted at specific individuals, organizations, or industries. The attackers often conduct thorough research to gather intelligence about the target before launching the attack.

4. Customized Malware: APT attacks frequently involve the use of custom-designed malware, tailored to the specific target environment. This makes it harder for traditional security tools to detect and mitigate the threat.

5. Stealthy Operations: APT attackers prioritize remaining stealthy and avoiding detection. They may use techniques such as lateral movement within a network, privilege escalation, and encryption to conceal their activities.

6. Long-Term Goals: APT attacks are not opportunistic or random; they are conducted with specific, long-term objectives. These objectives could include stealing intellectual property, gaining political advantage, or other strategic goals.

7. Multiple Phases: APT attacks often unfold in multiple phases, including initial reconnaissance, gaining access, maintaining persistence, lateral movement, and achieving the ultimate objective.

Defending against APT attacks requires a multi-layered approach, including robust cybersecurity measures, continuous monitoring, employee education on security best practices, and timely incident response capabilities. Organizations need to be proactive in their cybersecurity efforts to detect and mitigate APT threats effectively.