On Saturday 1 April 2023 at 04:19 UTC, a Slowloris targeted a news publisher customer in the UK. The attack peaked at 846.0 million requests per second and lasted 123 minutes. Traffic originated from 2093 autonomous systems in 54 countries, predominantly mobile carrier ranges.
| Vector | Slowloris |
| Peak | 846.0 million requests per second |
| Duration | 123 min |
| Time to mitigation | 0.664 s |
| Attack traffic reaching origin | 0.010% |
| 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 344 within 5 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
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Review allow-listed partner ranges quarterly.
- Enable authenticated origin pulls.
Could you share the dataset behind the percentages?
Any plans to support per-tenant limits keyed on a JWT claim?
Verified good bots and allow-listed partners bypass challenges entirely.
The point about origin IPs leaking through certificate transparency logs is underrated.
Thanks! Yes — the risk score and its components are included in every log record.