On Sunday 6 March 2022 at 07:10 UTC, a Slowloris targeted a tax authority portal customer in Western Europe. The attack peaked at 624.5 million requests per second and lasted 4 minutes. Traffic originated from 2541 autonomous systems in 90 countries, predominantly a rented booter service.
| Vector | Slowloris |
| Peak | 624.5 million requests per second |
| Duration | 4 min |
| Time to mitigation | 0.008 s |
| Attack traffic reaching origin | 0.086% |
| Legitimate traffic challenged | 0.08% |
Timeline
The attack was preceded by a competitor’s product launch. Request rates on the targeted routes exceeded their hourly baseline by a factor of 819 within 21 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
A brief increase in p99 latency of 101 ms during the first minute, then normal service.
Recommendations
- Enable authenticated origin pulls.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable log streaming to your SIEM for faster correlation.
Great write-up. We saw almost the same pattern on our login endpoint last month.
This matches what we see in iGaming around big matches.
Machine-readable ranges are at /ips.json and via the API.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.
Clear and practical, thanks.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Nice to read a vendor blog that admits what went wrong.