On Sunday 30 June 2024 at 10:37 UTC, a ACK flood targeted a healthcare portal customer in the Nordics. The attack peaked at 352.8 Gbps and lasted 3 minutes. Traffic originated from 661 autonomous systems in 80 countries, predominantly a headless-browser farm.
| Vector | ACK flood |
| Peak | 352.8 Gbps |
| Duration | 3 min |
| Time to mitigation | 0.354 s |
| Attack traffic reaching origin | 0.040% |
| Legitimate traffic challenged | 0.61% |
Timeline
The attack was preceded by an extortion email received two days earlier. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 33 points of presence.
What the customer saw
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Add a dedicated rate limit for the targeted route.
- Review allow-listed partner ranges quarterly.
- Enable authenticated origin pulls.
Solid runbook advice. The DNS-at-2am point hit home.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Great to hear, thanks for sharing your experience.
Could you share the dataset behind the percentages?
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.
Nice to read a vendor blog that admits what went wrong.
Nice to read a vendor blog that admits what went wrong.
Carpet bombing is nasty. Good to see a clear explanation of it.
Thanks — sharing this with our on-call team.
Would love a follow-up on how you handle HTTP/3 fingerprinting.