DNS DDos of the Day

My phone got a call recently from a systems administrator whose network was under attack. I was busy getting my twice-weekly dose of humility, but a couple hours later, my phone delivered the message.

The attacker was flooding their primary DNS server with requests for isc.org. This is a not-uncommon attack. As DDos attacks go, it's not terribly effective; it can overwhelm the DNS server's resources, but doesn't utterly destroy the victim's network. You can easily defend against this by...