On Wednesday 3 January 2024 at 23:24 UTC, a Slowloris targeted a electronics retail customer in the Benelux. The attack peaked at 371.1 million requests per second and lasted 96 minutes. Traffic originated from 1295 autonomous systems in 108 countries, predominantly residential proxy networks.
| Vector | Slowloris |
| Peak | 371.1 million requests per second |
| Duration | 96 min |
| Time to mitigation | 0.122 s |
| Attack traffic reaching origin | 0.076% |
| Legitimate traffic challenged | 0.80% |
Timeline
The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 827 within 30 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 222 ms during the first minute, then normal service.
Recommendations
- Review allow-listed partner ranges quarterly.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable authenticated origin pulls.
Our auditors asked for exactly this kind of incident evidence under DORA.
Thanks! Yes — the risk score and its components are included in every log record.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.
Thanks — sharing this with our on-call team.
Good question. We will cover that in a follow-up post.
Carpet bombing is nasty. Good to see a clear explanation of it.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Clear and practical, thanks.
Carpet bombing is nasty. Good to see a clear explanation of it.
Would love a follow-up on how you handle HTTP/3 fingerprinting.