In the context of personal computers, is it possible to attain "privacy and security" without control For example, can a "Big Tech" company attain "privacy and

In the context of personal computers, is it possible to attain "privacy and security" without control For example, can a "Big Tech" company attain "privacy and security" if it does not have control over its computers. What if it delegates control to someone else such as an individual home internet subscriber For another example, can an individual home internet subscriber attain "privacy and security" if he does not have control over his computers. What if the subscriber delegates control to a "Big Tech" company