Why is using administrative user a security problem?

[Aniej]

Why is it important to not run in the administrator mode? many people have said this to me now in different threads, but they always leave out the most important point, i.e., why doing so poses a problem?

On a similar note, I was in Safari prefs and was wondering what is the point of disabling open "safe" files in safari if I will be doing the exact same thing when I manually open it after I download the file?

 

[Richard Flynn]

One reason is here, that when running as Administrator, a poorly written (or malicious) installer program can cause problems without the user intervening (what should happen is the user has to enter his Admin password when anything vaguely system-important takes place, but because of a flaw this doesn't always happen when already running as Admin). The article gets a bit technical, but it's well written nevertheless.

I originally heard about this on MacBreak Weekly episode 7.

 

[SC68Cal]

Because you don't get it.

http://en.wikipedia.org/wiki/Principle_of_least_privilege