School me on how seemingly benign programs can harm security

[bennylava]

Hi all, new here. I didn't see a general questions forum, so I'll just put this here. I'm hoping someone can school me on the security holes that can/do occur in the programs we use. What brought this up was the fact that Micro$oft does not have access to the source code for the little apps (like say Candy Crush Saga) that the force on us. I've done the registry edit to stop this, and we'll see if it even sticks.



But that's just one example. What I'm actually trying to learn, is the various means and avenues that security can fail, in a random computer program. Any program. So take that candy crush game for instance. The one microsoft forces on us in Windows 10. What are all the possible source of a security breach? Below I'll make a list from my limited understanding.



1. The app itself is programmed to harm your security. The programmers deliberately put in code that harvests data, or installs other malicious applications that do so. All behind your back of course.



2. The app itself is so poorly written, that it actually has gaping security holes that can still be used by other evil 3rd party coders. They can sort of insert their code into the program, so now its doing things it was never intended to do. This could be completely unintentional by the developers of the app. Or not. Either way, its got some kind of security hole. This is something I don't understand, and hopefully someone else can sort of fill in the blanks for me here.



3. ??? Did I leave out anything? What are the other big security concerns, that could come in over the internet, that have to do with the seemingly benign programs that any user may wish to have on their computer?