On Sunday 12 February 2023 at 04:10 UTC, a TLS handshake exhaustion targeted a crypto exchange customer in the Benelux. The attack peaked at 252.2 million requests per second and lasted 61 minutes. Traffic originated from 3353 autonomous systems in 64 countries, predominantly misconfigured open reflectors.
| Vector | TLS handshake exhaustion |
| Peak | 252.2 million requests per second |
| Duration | 61 min |
| Time to mitigation | 0.043 s |
| Attack traffic reaching origin | 0.069% |
| Legitimate traffic challenged | 0.58% |
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 361 within 24 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.
- Enable log streaming to your SIEM for faster correlation.
- Enable authenticated origin pulls.