Threat Bulletin 1271: WebSocket connection flood against a healthcare portal platform in North America

On Monday 5 January 2026 at 16:28 UTC, a WebSocket connection flood targeted a healthcare portal customer in North America. The attack peaked at 37.5 million requests per second and lasted 32 minutes. Traffic originated from 3035 autonomous systems in 51 countries, predominantly residential proxy networks.

Vector WebSocket connection flood
Peak 37.5 million requests per second
Duration 32 min
Time to mitigation 0.949 s
Attack traffic reaching origin 0.017%
Legitimate traffic challenged 0.29%

Timeline

The attack was preceded by a hacktivist channel announcing the target. Request rates on the targeted routes exceeded their hourly baseline by a factor of 810 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

Checkout conversion was unchanged compared with the same hour of the previous week.

Recommendations

  • Lower challenge thresholds on authentication endpoints during high-risk events.
  • Keep origin IPs out of public DNS history.
  • Review allow-listed partner ranges quarterly.

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