On Friday 19 March 2021 at 10:49 UTC, a HTTP POST flood targeted a retail banking customer in Southeast Asia. The attack peaked at 238.9 million requests per second and lasted 59 minutes. Traffic originated from 1116 autonomous systems in 73 countries, predominantly mobile carrier ranges.
| Vector | HTTP POST flood |
| Peak | 238.9 million requests per second |
| Duration | 59 min |
| Time to mitigation | 0.391 s |
| Attack traffic reaching origin | 0.003% |
| Legitimate traffic challenged | 0.68% |
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 625 within 17 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
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Add a dedicated rate limit for the targeted route.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Keep origin IPs out of public DNS history.