Indicators of Compromise (IoCs) are pieces of evidence that suggest a computer system or network has been breached by malicious activity. These clues can include unusual filenames, suspicious IP addresses, unfamiliar server domains, or specific code fragments found in system logs. Security professionals use IoCs to detect, investigate, and respond to cybersecurity incidents by identifying patterns that match known threats. By monitoring for these warning signs, organizations can quickly spot and contain potential attacks, minimizing damage and preventing further compromise.