Malware
Rootkit
Malware that buries itself deep in the system so that it hides from the user and from many security programs.
A rootkit gives its owner high-level control and then hides the traces: its files, its processes, sometimes the fact that anything changed. Because it sits so deep, it is hard to be sure a normal clean-up removed it.
It is uncommon for ordinary users. If one is suspected, the safe answer is usually to save your personal files, then reinstall the system from a trusted source.
What to do
- Keep the system and its startup protection updated.
- Do not run programs that ask for full administrator rights without a clear reason.
- If you suspect one, back up your files and reinstall the system.