On Sunday 29 August 2021 at 02:07 UTC, a UDP reflection (DNS) targeted a electronics retail customer in the UK. The attack peaked at 227.8 Gbps and lasted 11 minutes. Traffic originated from 2723 autonomous systems in 109 countries, predominantly compromised cloud VMs.
| Vector | UDP reflection (DNS) |
| Peak | 227.8 Gbps |
| Duration | 11 min |
| Time to mitigation | 0.023 s |
| Attack traffic reaching origin | 0.008% |
| Legitimate traffic challenged | 0.76% |
Timeline
The attack was preceded by an extortion email received two days earlier. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 24 points of presence.
What the customer saw
No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.
Recommendations
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.
- Enable log streaming to your SIEM for faster correlation.
Solid runbook advice. The DNS-at-2am point hit home.
Is the risk score exposed in the logs so we can build our own dashboards on it?