On Friday 23 June 2023 at 23:57 UTC, a credential stuffing targeted a tax authority portal customer in Iberia. The attack peaked at 296.9 million requests per second and lasted 54 minutes. Traffic originated from 2827 autonomous systems in 19 countries, predominantly mobile carrier ranges.
| Vector | credential stuffing |
| Peak | 296.9 million requests per second |
| Duration | 54 min |
| Time to mitigation | 0.065 s |
| Attack traffic reaching origin | 0.066% |
| Legitimate traffic challenged | 0.51% |
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 891 within 33 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.
- Enable log streaming to your SIEM for faster correlation.
- Keep origin IPs out of public DNS history.
The point about origin IPs leaking through certificate transparency logs is underrated.
Machine-readable ranges are at /ips.json and via the API.