On Thursday 9 September 2021 at 12:48 UTC, a TLS handshake exhaustion targeted a online payments customer in Southeast Asia. The attack peaked at 419.7 million requests per second and lasted 153 minutes. Traffic originated from 1040 autonomous systems in 106 countries, predominantly a headless-browser farm.
| Vector | TLS handshake exhaustion |
| Peak | 419.7 million requests per second |
| Duration | 153 min |
| Time to mitigation | 0.914 s |
| Attack traffic reaching origin | 0.032% |
| Legitimate traffic challenged | 0.52% |
Timeline
The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 223 within 30 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
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Enable authenticated origin pulls.
- Enable log streaming to your SIEM for faster correlation.
- Keep origin IPs out of public DNS history.
Our auditors asked for exactly this kind of incident evidence under DORA.