Threat Bulletin 1290: Slowloris against a tax authority portal platform in the Nordics

On Sunday 1 February 2026 at 07:36 UTC, a Slowloris targeted a tax authority portal customer in the Nordics. The attack peaked at 118.6 million requests per second and lasted 132 minutes. Traffic originated from 494 autonomous systems in 107 countries, predominantly a rented booter service.

Vector Slowloris
Peak 118.6 million requests per second
Duration 132 min
Time to mitigation 0.516 s
Attack traffic reaching origin 0.021%
Legitimate traffic challenged 0.71%

Timeline

The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 257 within 36 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

  • Add a dedicated rate limit for the targeted route.
  • Review allow-listed partner ranges quarterly.
  • Keep origin IPs out of public DNS history.

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