Now that's a good question, I aint a good enough geek to explain it!
There are lots of ways for those in the know to steal my personal details or break into my car or house I don't always understand how they do it but I know they can!
Like Euro locks a piece of p**s to break into once you know how, but now there are anti snap or anti bump versions you can update to.
As I understand a security program may not spot a genuine microsoft program that has been exploited because it assumes it is ok, after all its been using it for ages
Where as a new virus or malware program will be spotted.