[Windows Central Question]

which is the best antivirus software for Lumia 520 phone?

[Chintan Gohel]

which is the best antivirus software for Lumia 520 phone?

you don't need an antivirus for your phone as it cannot be attacked

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[RumoredNow]

Here is some good reading that applies to WP 8/8.1 and still works for W10M.

Should I worry about viruses or malware? - Microsoft Community

[CozyPlanes]

You dont need an antivirus for wp because each program is sandboxed which means the virus cant infect the system.