DDoS attacks generally rely on big numbers to get results. Hundreds of thousands of devices, millions of IP addresses all unleashing coordinated blasts of data at another device to bring it to its knees. A BlackNurse denial-of-service attack doesn’t need a massive army of zombies to be effective.
The BlackNurse attack is much more efficient than the DDoS attacks that crippled security researcher Brian Krebs’ website and the DNS servers at Dyn. Some recent DDoS attacks have seen traffic peak at more than 1 Tbps. A BlackNurse attack has the ability to disrupt by sending just a fraction of that volume. As little as 21 Mbps can be enough to take down a firewall, according to security firm Netresec.
What’s different about BlackNurse that allows it to inflict so much damage with so little effort? It’s the type of traffic it utilizes. BlackNurse directs Internet Control Message Protocol (ICMP) packets, which have been used in other DDoS attacks in the past. BlackNurse uses a specific type — ICMP type 3 code 3.
An attack from a single laptop could, theoretically, knock an entire business offline, though it’s not likely to be a very large business. In their blog post, Netresec calls out firewalls made by Cisco, Palo Alto Networks, Sonicwall, and Zyxel as being at risk. Most of the devices Netresec reports as being vulnerable to a BlackNurse attack (like the Cisco ASA 5506 and Zyxel Zywall USG50) were designed for small office or home office use.
That said, TDC, a Denmark-based company that offers DDoS protection services to businesses, has seen enterprise-grade gear impacted. “We had expected that professional firewall equipment would be able to handle the attack,” they wrote, adding that they’ve seen around 100 of these attacks launched against their customers.
TDC also notes that BlackNurse has the potential to create a lot of havoc. In Denmark’s IP space alone they discovered 1.7 million devices that respond to the ICMP requests that the BlackNurse attack leverages. If even a small percentage of those 1.7 million devices are vulnerable, the effects of a coordinated, large-scale attack could be disastrous. And that’s just Denmark.