how secure is internet security?

I am new to the internet…know very little about internet buying online….i really like to buying things from the internet..but scare….cause a website like cnn, yahoo, and amazon get hacks, how will i know i will not get hack and how do i know iwill get hack by a hacker and trust them with my credit card and social security numbers online? are there any software program security out there that you know, i can buy to put into my systms…let me know that i am been hack or going to be hacking my a hacker? its really a stupid questions but please help me out?