Advanced Persistent Threats (APTs) pose cybersecurity threats to the energy sector, specifically targeting Industrial Control Systems (ICS). APTs use sophisticated methods for prolonged cyber-attacks that find system vulnerabilities to enable operational takeover, financial damage, and security risks at a national level. The study investigates how APTs persist and how energy infrastructure security withstands them while detailing their effects on security resilience for energy systems.The study adopts a systematic literature review (SLR) methodology to analyse peer-reviewed research published between 2015 and 2025 about APT tactics, techniques, and procedures (TTPS) through the MITRE ATT&CK Matrix for ICS. It also presents findings about ICS attack methods alongside their security implications and identifies flaws in current mitigation strategies. It then suggests adaptive detection methods before presenting a framework to improve resistance against persistent threats. Traditional cybersecurity approaches prove inadequate for dealing with the current evolution of APT tactics, thus demanding immediate implementation of proactive detection mechanisms. This research supports continuous monitoring, proactive security measures, and artificial intelligence systems detecting irregular activities. The study merges threat intelligence while providing functional security upgrades for Industrial Control Systems infrastructure. Future studies should empirically test the proposed mitigation strategies to strengthen APT defence measures within the energy sector.