spyware

US /ˈspaɪ.wer/
UK /ˈspaɪ.wer/
"spyware" picture
1.

software that enables a user to obtain covert information about another's computer activities by transmitting data covertly from their hard drive.

:
Always install antivirus software to protect against spyware.
The company's network was compromised by a sophisticated spyware attack.