not using CCleaner would be a start. pay attention to the version of what you are using and avoid using things on auto-update or on a version which haven't bee

not using CCleaner would be a start. pay attention to the version of what you are using and avoid using things on auto-update or on a version which haven't been battleproof. use linux and check the source code of everything you run... but it's a lot of work so basically I don't think you could've done much, nor most of the people can unless you would accept living in a very walled and time-consuming computer setup