On Thursday 15 May 2025 at 23:14 UTC, a cache-busting query flood targeted a B2B SaaS customer in the Nordics. The attack peaked at 440.8 million requests per second and lasted 18 minutes. Traffic originated from 75 autonomous systems in 58 countries, predominantly misconfigured open reflectors.
| Vector | cache-busting query flood |
| Peak | 440.8 million requests per second |
| Duration | 18 min |
| Time to mitigation | 0.018 s |
| Attack traffic reaching origin | 0.031% |
| Legitimate traffic challenged | 0.37% |
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 196 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
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.
- Add a dedicated rate limit for the targeted route.