On Thursday 9 October 2025 at 23:29 UTC, a Slowloris targeted a tax authority portal customer in the Benelux. The attack peaked at 555.2 million requests per second and lasted 117 minutes. Traffic originated from 2987 autonomous systems in 67 countries, predominantly misconfigured open reflectors.
| Vector | Slowloris |
| Peak | 555.2 million requests per second |
| Duration | 117 min |
| Time to mitigation | 0.009 s |
| Attack traffic reaching origin | 0.047% |
| Legitimate traffic challenged | 0.08% |
Timeline
The attack was preceded by an extortion email received two days earlier. Request rates on the targeted routes exceeded their hourly baseline by a factor of 565 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
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Review allow-listed partner ranges quarterly.
- Add a dedicated rate limit for the targeted route.