On Saturday 16 October 2021 at 19:46 UTC, a TLS handshake exhaustion targeted a municipal services customer in Central Europe. The attack peaked at 132.7 million requests per second and lasted 131 minutes. Traffic originated from 1282 autonomous systems in 66 countries, predominantly mobile carrier ranges.
| Vector | TLS handshake exhaustion |
| Peak | 132.7 million requests per second |
| Duration | 131 min |
| Time to mitigation | 0.598 s |
| Attack traffic reaching origin | 0.079% |
| Legitimate traffic challenged | 0.44% |
Timeline
The attack was preceded by a publicly announced sales event. Request rates on the targeted routes exceeded their hourly baseline by a factor of 807 within 27 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
- 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.