A person who gains unauthorised access to computer systems or data without permission. In insurance terms, this includes both external attackers (like criminals or foreign actors) and internal threats (like dishonest employees). When a hacker breaches your systems, cyber insurance typically covers the costs of investigating the attack, fixing systems, notifying affected customers, and lost income during downtime. However, coverage may require proof that you had reasonable security measures in place, like strong passwords and security software. Some policies won't cover attacks by foreign governments or incidents caused by poor security practices.