On Tuesday 20 April 2021 at 07:10 UTC, a HTTP POST flood targeted a education platform customer in the UK. The attack peaked at 589.4 million requests per second and lasted 52 minutes. Traffic originated from 4011 autonomous systems in 96 countries, predominantly a rented booter service.
| Vector | HTTP POST flood |
| Peak | 589.4 million requests per second |
| Duration | 52 min |
| Time to mitigation | 0.140 s |
| Attack traffic reaching origin | 0.073% |
| Legitimate traffic challenged | 0.79% |
Timeline
The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 644 within 13 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
- Add a dedicated rate limit for the targeted route.
- Enable log streaming to your SIEM for faster correlation.
- Keep origin IPs out of public DNS history.