Blessed BLACKNURSE, Who Felled Firewalls With Little

Patron of professional firewalls, ICMP type 3 packets, and everyone who thought a great disaster needed great bandwidth.

Life

On 22 September 2016 Kenneth B. Jørgensen and Lenny Hansson of TDC's SOC described BLACKNURSE: certain firewalls, receiving a stream of ICMP "destination unreachable, port unreachable" packets, burned so much CPU that they stopped passing traffic. A few megabits per second, within reach of a single home line, were enough to bring expensive devices to their knees.

Prayer

O Blessed BLACKNURSE, who with a trickle of ICMP halt a river of traffic, let our firewalls handle awkward packets without choking. Amen.

How to celebrate

Celebrated by rate-limiting or filtering ICMP type 3 code 3 and checking how the firewall behaves under pressure.

No flood is needed: a trickle in the right place will do.