On Thursday 23 October 2025 at 23:58 UTC, a TLS handshake exhaustion targeted a healthcare portal customer in Central Europe. The attack peaked at 383.1 million requests per second and lasted 190 minutes. Traffic originated from 1046 autonomous systems in 76 countries, predominantly compromised cloud VMs.
| Vector | TLS handshake exhaustion |
| Peak | 383.1 million requests per second |
| Duration | 190 min |
| Time to mitigation | 0.689 s |
| Attack traffic reaching origin | 0.055% |
| Legitimate traffic challenged | 0.48% |
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 718 within 14 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
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.