Threat Bulletin 1244: credential stuffing against a healthcare portal platform in Western Europe

On Saturday 29 November 2025 at 06:22 UTC, a credential stuffing targeted a healthcare portal customer in Western Europe. The attack peaked at 735.4 million requests per second and lasted 68 minutes. Traffic originated from 1175 autonomous systems in 25 countries, predominantly hijacked home routers.

Vector credential stuffing
Peak 735.4 million requests per second
Duration 68 min
Time to mitigation 0.208 s
Attack traffic reaching origin 0.020%
Legitimate traffic challenged 0.57%

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 853 within 17 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.
  • Add a dedicated rate limit for the targeted route.
  • Keep origin IPs out of public DNS history.

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