The good news? There are ways to fight against BlackNurse. TDC recommends setting up software filters to prevent this kind of flooding. Also, this is mainly a concern with firewall makers that allow ICMP packets from outside. Palo Alto, for instance, notes that its firewalls drop those kinds of requests by default -- unless you change the settings and don't follow its guidelines for anti-flood protection, you're safe. Cisco doesn't see a major issue, either.

The danger is that not every firewall is guaranteed to follow similar rules, and that some businesses may have reasons to tweak their settings to let ICMP data in. Even if the threat isn't high, the discovery is a reminder that denial of service attacks can take many shapes. In the right circumstances, one person at home could be just as dangerous as a dedicated cyberattack group.