“Format the hard drive and do a clean install.”
When you get a cold what do you do? Remove a lung and sand blast it? Gargle with lye?
Formating a drive is not practical for most people.
LMAO!
In some cases, the infections can be so bad that it will take longer to wipe the disk and reinstall the OS than to completely clean it, and then there's the little thought that just maybe if it was that badly compromised, you might not have gotten it all. The rule for C2 security is that once the trusted computer base has been compromised, you're done: The only way to trust the computer again is to wipe it and start all over. Of course most people never need that level of security.
Mark