Typically, a foistware infection would be triggered by your careless mouse click(s). Examples are:
- You downloaded and ran some downware or CPI powered setup file directly without a security check/scan, e.g., some FakeAlerts like pop-ups.
- You just clicked the "I Accept" button or "Next" button during some heavily sponsored or bloated install process.
- You put your whole trust in some legal software, which would also install extra products without your permission, e.g., this Reimage Repair.
Learn more on how to secure your personal computer from the mentioned term, PUP or PUA.