On Tuesday 18 November 2025 at 22:07 UTC, a ACK flood targeted a healthcare portal customer in the Nordics. The attack peaked at 317.5 Gbps and lasted 49 minutes. Traffic originated from 2299 autonomous systems in 27 countries, predominantly residential proxy networks.
| Vector | ACK flood |
| Peak | 317.5 Gbps |
| Duration | 49 min |
| Time to mitigation | 0.776 s |
| Attack traffic reaching origin | 0.054% |
| Legitimate traffic challenged | 0.80% |
Timeline
The attack was preceded by a breaking political story. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 38 points of presence.
What the customer saw
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Review allow-listed partner ranges quarterly.
- Add a dedicated rate limit for the targeted route.
- Enable authenticated origin pulls.
Solid runbook advice. The DNS-at-2am point hit home.
Nice to read a vendor blog that admits what went wrong.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Could you share the dataset behind the percentages?
Would love a follow-up on how you handle HTTP/3 fingerprinting.
Verified good bots and allow-listed partners bypass challenges entirely.
Clear and practical, thanks.
Would love a follow-up on how you handle HTTP/3 fingerprinting.