On Friday 9 July 2021 at 15:13 UTC, a ACK flood targeted a crypto exchange customer in the UK. The attack peaked at 238.0 Gbps and lasted 184 minutes. Traffic originated from 948 autonomous systems in 57 countries, predominantly compromised cloud VMs.
| Vector | ACK flood |
| Peak | 238.0 Gbps |
| Duration | 184 min |
| Time to mitigation | 0.796 s |
| Attack traffic reaching origin | 0.073% |
| Legitimate traffic challenged | 0.07% |
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 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
- Keep origin IPs out of public DNS history.
- Add a dedicated rate limit for the targeted route.
- Review allow-listed partner ranges quarterly.