On Thursday 26 August 2021 at 08:18 UTC, a Slowloris targeted a electronics retail customer in Latin America. The attack peaked at 613.3 million requests per second and lasted 11 minutes. Traffic originated from 850 autonomous systems in 68 countries, predominantly misconfigured open reflectors.
| Vector | Slowloris |
| Peak | 613.3 million requests per second |
| Duration | 11 min |
| Time to mitigation | 0.947 s |
| Attack traffic reaching origin | 0.066% |
| Legitimate traffic challenged | 0.77% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 489 within 38 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
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.
The point about origin IPs leaking through certificate transparency logs is underrated.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Do you publish the edge IP ranges in a machine-readable format?
Machine-readable ranges are at /ips.json and via the API.
Clear and practical, thanks.
Great to hear, thanks for sharing your experience.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.