  Billions of wireless devices are foreseen to participate in big data
aggregation and smart automation in order to interface the cyber and physical
worlds. Such large-scale ultra-dense wireless connectivity is vulnerable to
malicious software (malware) epidemics. Malware worms can exploit multi-hop
wireless connectivity to stealthily diffuse throughout the wireless network
without being noticed to security servers at the core network. Compromised
devices can then be used by adversaries to remotely launch cyber attacks that
cause large-scale critical physical damage and threaten public safety. This
article overviews the types, threats, and propagation models for malware
epidemics in large-scale wireless networks (LSWN). Then, the article proposes a
novel and cost efficient countermeasure against malware epidemics in LSWN,
denoted as spatial firewalls. It is shown that equipping a strategically
selected small portion (i.e., less than 10\%) of the devices with
state-of-the-art security mechanisms is sufficient to create spatially secured
zones that quarantine malware epidemics. Quarantined infected devices are then
cured by on-demand localized software patching. To this end, several firewall
deployment strategies are discussed and compared.
