Threat Bulletin 1234: HTTP GET flood against a tax authority portal platform in North America

On Friday 14 November 2025 at 22:19 UTC, a HTTP GET flood targeted a tax authority portal customer in North America. The attack peaked at 110.4 million requests per second and lasted 38 minutes. Traffic originated from 422 autonomous systems in 43 countries, predominantly hijacked home routers.

Vector HTTP GET flood
Peak 110.4 million requests per second
Duration 38 min
Time to mitigation 0.271 s
Attack traffic reaching origin 0.015%
Legitimate traffic challenged 0.62%

Timeline

The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 745 within 22 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.
  • Add a dedicated rate limit for the targeted route.

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