Threat Bulletin 1322: WebSocket connection flood against a retail banking platform in the Benelux

On Thursday 19 March 2026 at 10:50 UTC, a WebSocket connection flood targeted a retail banking customer in the Benelux. The attack peaked at 789.4 million requests per second and lasted 90 minutes. Traffic originated from 2830 autonomous systems in 6 countries, predominantly a rented booter service.

Vector WebSocket connection flood
Peak 789.4 million requests per second
Duration 90 min
Time to mitigation 0.704 s
Attack traffic reaching origin 0.053%
Legitimate traffic challenged 0.01%

Timeline

The attack was preceded by no stated motive. Request rates on the targeted routes exceeded their hourly baseline by a factor of 111 within 26 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

A brief increase in p99 latency of 111 ms during the first minute, then normal service.

Recommendations

  • Enable log streaming to your SIEM for faster correlation.
  • Enable authenticated origin pulls.
  • Lower challenge thresholds on authentication endpoints during high-risk events.

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