[WPCentral Question]

I just want to install an antivirus

[Pete]

No, you don't want to install an anti-virus. There's no way that any programs can run on your phone without them coming directly from Microsoft.

If you have a problem that leads you to think you have a virus, you'll need to tell us the symptoms as it'll be caused by something else.

[Ndabezayo Dlamini]

The phone would sometimes enlarge the icons or freeze on its own. what do you think is the cause?

[Pete]

Sounds like you've enabled the screen magnifier options in settings->ease of access.

Read further here.

Accessibility on Windows Phone | Windows Phone How-to (United States)

If you don't need the screen magnifier, turn it off.

[8mir]

You will don't need to install any anti virus because the apps of windows store are scan by microsoft

[Anjan Some]

I have a question.. Can't a virus enter through the memory card???

[Pete]

I have a question.. Can't a virus enter through the memory card???

No.

Although it's possible to copy files that contain viruses onto a memory card, there's no way that code or script can execute on a phone. The only code that can execute on the phone is apps obtained through the official Windows Phone Store or updates sent directly from Microsoft.