On Tuesday 5 April 2022 at 13:43 UTC, a Slowloris targeted a tax authority portal customer in the UK. The attack peaked at 13.0 million requests per second and lasted 96 minutes. Traffic originated from 3120 autonomous systems in 67 countries, predominantly hijacked home routers.
| Vector | Slowloris |
| Peak | 13.0 million requests per second |
| Duration | 96 min |
| Time to mitigation | 0.060 s |
| Attack traffic reaching origin | 0.031% |
| Legitimate traffic challenged | 0.28% |
Timeline
The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 134 within 15 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
- Review allow-listed partner ranges quarterly.
- Enable authenticated origin pulls.
- Enable log streaming to your SIEM for faster correlation.