On Wednesday 11 August 2021 at 08:41 UTC, a UDP reflection (DNS) targeted a municipal services customer in North America. The attack peaked at 359.5 Gbps and lasted 71 minutes. Traffic originated from 2574 autonomous systems in 37 countries, predominantly residential proxy networks.
| Vector | UDP reflection (DNS) |
| Peak | 359.5 Gbps |
| Duration | 71 min |
| Time to mitigation | 0.186 s |
| Attack traffic reaching origin | 0.012% |
| Legitimate traffic challenged | 0.01% |
Timeline
The attack was preceded by a breaking political story. 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
A brief increase in p99 latency of 194 ms during the first minute, then normal service.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.