Malicious software, including viruses, worms, trojans, and ransomware, is deployed to infiltrate target systems. Spyware is specifically designed to covertly monitor user activity, capture keystrokes, and exfiltrate data. Nation-state actors often develop custom malware with specialized capabilities like Stuxnet, which targeted Iranian nuclear facilities, or Flame, which collected intelligence across the Middle East. Commercial spyware such as Pegasus, developed by NSO Group, has been used by governments worldwide to monitor journalists, activists, and political opponents. Malware delivery methods continue to evolve, leveraging zero-day vulnerabilities, supply chain compromises, and legitimate software update mechanisms to reach their targets.