Threat Bulletin 1311: search endpoint flood against a tax authority portal platform in Western Europe

On Tuesday 3 March 2026 at 22:35 UTC, a search endpoint flood targeted a tax authority portal customer in Western Europe. The attack peaked at 630.0 million requests per second and lasted 144 minutes. Traffic originated from 3117 autonomous systems in 67 countries, predominantly misconfigured open reflectors.

Vector search endpoint flood
Peak 630.0 million requests per second
Duration 144 min
Time to mitigation 0.704 s
Attack traffic reaching origin 0.032%
Legitimate traffic challenged 0.75%

Timeline

The attack was preceded by a competitor’s product launch. Request rates on the targeted routes exceeded their hourly baseline by a factor of 679 within 15 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 log streaming to your SIEM for faster correlation.
  • Enable authenticated origin pulls.
  • Keep origin IPs out of public DNS history.

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