Threat Bulletin 0407: login endpoint flood against a municipal services platform in the Benelux

On Tuesday 13 September 2022 at 22:40 UTC, a login endpoint flood targeted a municipal services customer in the Benelux. The attack peaked at 372.6 million requests per second and lasted 172 minutes. Traffic originated from 3245 autonomous systems in 18 countries, predominantly residential proxy networks.

Vector login endpoint flood
Peak 372.6 million requests per second
Duration 172 min
Time to mitigation 0.319 s
Attack traffic reaching origin 0.079%
Legitimate traffic challenged 0.19%

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 198 within 28 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

No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.

Recommendations

  • Enable log streaming to your SIEM for faster correlation.
  • Review allow-listed partner ranges quarterly.
  • Lower challenge thresholds on authentication endpoints during high-risk events.

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