I use the Marketplace but I also use other repositorios… and I do hack it… but I guess I investigate before I do something and, of course, I always do my backup copy before any major change 
Having said that, a default user doesn’t have a root access on Android, you need to unlock it specifically. So if you go with the regular updates, you should be fine… which doesn’t mean that you can’t get virus (in any smart phone). It is a case that there are not so many.
Actually nokia lumia has the internet explorer 9 & it’s doesn’t support opera browser.
If you have any problem then you can switch it to Nokia Xpress Browser its same like the opera browser.
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This for me is where the iPhone shines in this department. I like how on the iPhone you don’t need to worry about this sort of stuff
You always have to worry about these things, iPhone or not
Hello guys…
Some smart phone have internal antivirus protected apps. If not available then you may download from internet.