On Friday 10 December 2021 at 06:06 UTC, a cache-busting query flood targeted a municipal services customer in Western Europe. The attack peaked at 185.3 million requests per second and lasted 114 minutes. Traffic originated from 1411 autonomous systems in 13 countries, predominantly a Mirai-derived IoT botnet.
| Vector | cache-busting query flood |
| Peak | 185.3 million requests per second |
| Duration | 114 min |
| Time to mitigation | 0.432 s |
| Attack traffic reaching origin | 0.075% |
| Legitimate traffic challenged | 0.42% |
Timeline
The attack was preceded by a ransom note demanding payment in Monero. Request rates on the targeted routes exceeded their hourly baseline by a factor of 312 within 36 seconds. The risk score of participating clients crossed the challenge threshold automatically and proof-of-work difficulty rose with origin load.
What the customer saw
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Review allow-listed partner ranges quarterly.
- Add a dedicated rate limit for the targeted route.
- Enable log streaming to your SIEM for faster correlation.
The point about origin IPs leaking through certificate transparency logs is underrated.