On Saturday 11 December 2021 at 21:54 UTC, a credential stuffing targeted a municipal services customer in the UK. The attack peaked at 589.9 million requests per second and lasted 75 minutes. Traffic originated from 2401 autonomous systems in 72 countries, predominantly mobile carrier ranges.
| Vector | credential stuffing |
| Peak | 589.9 million requests per second |
| Duration | 75 min |
| Time to mitigation | 0.422 s |
| Attack traffic reaching origin | 0.087% |
| Legitimate traffic challenged | 0.80% |
Timeline
The attack was preceded by a ransom note demanding payment in Monero. Request rates on the targeted routes exceeded their hourly baseline by a factor of 177 within 11 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
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.