On Sunday 14 March 2021 at 21:48 UTC, a CLDAP reflection targeted a municipal services customer in Western Europe. The attack peaked at 123.1 Gbps and lasted 160 minutes. Traffic originated from 193 autonomous systems in 57 countries, predominantly misconfigured open reflectors.
| Vector | CLDAP reflection |
| Peak | 123.1 Gbps |
| Duration | 160 min |
| Time to mitigation | 0.132 s |
| Attack traffic reaching origin | 0.079% |
| Legitimate traffic challenged | 0.29% |
Timeline
The attack was preceded by a hacktivist channel announcing the target. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 21 points of presence.
What the customer saw
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Review allow-listed partner ranges quarterly.
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable log streaming to your SIEM for faster correlation.
Nice to read a vendor blog that admits what went wrong.
Verified good bots and allow-listed partners bypass challenges entirely.
Carpet bombing is nasty. Good to see a clear explanation of it.
Great to hear, thanks for sharing your experience.
Would love a follow-up on how you handle HTTP/3 fingerprinting.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.
Verified good bots and allow-listed partners bypass challenges entirely.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.
Is the risk score exposed in the logs so we can build our own dashboards on it?
How do you avoid challenging uptime monitors and partners?
The point about origin IPs leaking through certificate transparency logs is underrated.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.