On Monday 24 February 2025 at 10:59 UTC, a GRE flood targeted a healthcare portal customer in Iberia. The attack peaked at 210.8 Gbps and lasted 126 minutes. Traffic originated from 806 autonomous systems in 77 countries, predominantly misconfigured open reflectors.
| Vector | GRE flood |
| Peak | 210.8 Gbps |
| Duration | 126 min |
| Time to mitigation | 0.082 s |
| Attack traffic reaching origin | 0.029% |
| Legitimate traffic challenged | 0.69% |
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 20 points of presence.
What the customer saw
A brief increase in p99 latency of 179 ms during the first minute, then normal service.
Recommendations
- Enable authenticated origin pulls.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Add a dedicated rate limit for the targeted route.
Nice to read a vendor blog that admits what went wrong.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.