On Tuesday 7 December 2021 at 19:03 UTC, a GRE flood targeted a education platform customer in the Middle East. The attack peaked at 12.5 Gbps and lasted 179 minutes. Traffic originated from 2431 autonomous systems in 68 countries, predominantly misconfigured open reflectors.
| Vector | GRE flood |
| Peak | 12.5 Gbps |
| Duration | 179 min |
| Time to mitigation | 0.422 s |
| Attack traffic reaching origin | 0.037% |
| Legitimate traffic challenged | 0.59% |
Timeline
The attack was preceded by no stated motive. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 13 points of presence.
What the customer saw
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Keep origin IPs out of public DNS history.
- Lower challenge thresholds on authentication endpoints during high-risk events.
Thanks — sharing this with our on-call team.
Verified good bots and allow-listed partners bypass challenges entirely.
Great write-up. We saw almost the same pattern on our login endpoint last month.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Great write-up. We saw almost the same pattern on our login endpoint last month.
Great to hear, thanks for sharing your experience.
How do you avoid challenging uptime monitors and partners?
The point about origin IPs leaking through certificate transparency logs is underrated.
Verified good bots and allow-listed partners bypass challenges entirely.
How do you avoid challenging uptime monitors and partners?
How does the proof-of-work challenge behave on older Android devices? Any numbers below Android 10?
Interesting that most attacks are under ten minutes. Our experience is similar.
Good question. We will cover that in a follow-up post.