Threat Bulletin 1288: ACK flood against a municipal services platform in the Benelux

On Thursday 29 January 2026 at 20:06 UTC, a ACK flood targeted a municipal services customer in the Benelux. The attack peaked at 280.4 Gbps and lasted 140 minutes. Traffic originated from 4031 autonomous systems in 51 countries, predominantly a Mirai-derived IoT botnet.

Vector ACK flood
Peak 280.4 Gbps
Duration 140 min
Time to mitigation 0.389 s
Attack traffic reaching origin 0.057%
Legitimate traffic challenged 0.12%

Timeline

The attack was preceded by a competitor’s product launch. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 20 points of presence.

What the customer saw

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

Recommendations

  • Review allow-listed partner ranges quarterly.
  • Lower challenge thresholds on authentication endpoints during high-risk events.
  • Keep origin IPs out of public DNS history.

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