On Monday 28 August 2023 at 09:05 UTC, a Slowloris targeted a online payments customer in North America. The attack peaked at 848.8 million requests per second and lasted 151 minutes. Traffic originated from 2415 autonomous systems in 114 countries, predominantly misconfigured open reflectors.
| Vector | Slowloris |
| Peak | 848.8 million requests per second |
| Duration | 151 min |
| Time to mitigation | 0.713 s |
| Attack traffic reaching origin | 0.002% |
| Legitimate traffic challenged | 0.53% |
Timeline
The attack was preceded by an extortion email received two days earlier. Request rates on the targeted routes exceeded their hourly baseline by a factor of 425 within 39 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
- Keep origin IPs out of public DNS history.
- Review allow-listed partner ranges quarterly.
- Lower challenge thresholds on authentication endpoints during high-risk events.