On Saturday 6 November 2021 at 17:16 UTC, a TLS handshake exhaustion targeted a video streaming customer in North America. The attack peaked at 457.5 million requests per second and lasted 100 minutes. Traffic originated from 2386 autonomous systems in 83 countries, predominantly a headless-browser farm.
| Vector | TLS handshake exhaustion |
| Peak | 457.5 million requests per second |
| Duration | 100 min |
| Time to mitigation | 0.060 s |
| Attack traffic reaching origin | 0.005% |
| Legitimate traffic challenged | 0.67% |
Timeline
The attack was preceded by a competitor’s product launch. Request rates on the targeted routes exceeded their hourly baseline by a factor of 687 within 19 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 74 ms during the first minute, then normal service.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Add a dedicated rate limit for the targeted route.
- Review allow-listed partner ranges quarterly.