On Monday 29 November 2021 at 09:52 UTC, a UDP reflection (DNS) targeted a online payments customer in the Benelux. The attack peaked at 184.8 Gbps and lasted 84 minutes. Traffic originated from 4089 autonomous systems in 73 countries, predominantly misconfigured open reflectors.
| Vector | UDP reflection (DNS) |
| Peak | 184.8 Gbps |
| Duration | 84 min |
| Time to mitigation | 0.900 s |
| Attack traffic reaching origin | 0.053% |
| Legitimate traffic challenged | 0.52% |
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 40 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.
- Enable log streaming to your SIEM for faster correlation.
- Lower challenge thresholds on authentication endpoints during high-risk events.
Could you share the dataset behind the percentages?
Would love a follow-up on how you handle HTTP/3 fingerprinting.
Machine-readable ranges are at /ips.json and via the API.
How does the proof-of-work challenge behave on older Android devices? Any numbers below Android 10?
Would love a follow-up on how you handle HTTP/3 fingerprinting.
Solid runbook advice. The DNS-at-2am point hit home.