Threat Bulletin 1221: GRE flood against a municipal services platform in the Benelux

On Tuesday 28 October 2025 at 09:10 UTC, a GRE flood targeted a municipal services customer in the Benelux. The attack peaked at 357.3 Gbps and lasted 35 minutes. Traffic originated from 1854 autonomous systems in 59 countries, predominantly compromised cloud VMs.

Vector GRE flood
Peak 357.3 Gbps
Duration 35 min
Time to mitigation 0.344 s
Attack traffic reaching origin 0.090%
Legitimate traffic challenged 0.37%

Timeline

The attack was preceded by a publicly announced sales event. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 28 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

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

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