In pandemic disease era, facemask is a effective means to protect being infected via airborne transmission. This is usually voluntary but in extreme situation, facemask is mandated by authority for presence in the public.
Facemask serves two-folded protection: (a) protecting an individual from infected or (b) containing an infected individual from spreading the disease.
In cyber world, similar protection philosophy applies. A device has platform protection (like host firewall) from being attacked by compromised device in the network, or limits its attack to other network neighborhood, if compromised. Further peer isolation in the network, usually enforced in wireless network, will enhance this protection.
When formulating protection, we need to think in all perspectives.