Types
Spyware
Surveillance malware that covertly monitors a target — messages, calls, location and microphone — often deployed against individuals.
Spyware covertly surveils a target. Commercial and state-grade spyware can read messages and email, track location, and silently activate the microphone and camera. Unlike mass-market malware, advanced spyware is often used in targeted operations against journalists, activists and officials.
Mobile mercenary spyware
The most capable modern spyware targets smartphones via zero-click exploits that require no user interaction. Pegasus is the best-known example, sold to governments as "lawful intercept" tooling but repeatedly found on civil-society devices.
Defense
Keep devices patched, enable hardened/lockdown modes, reboot regularly, and — for high-risk users — rely on forensic checks of device logs.