On Monday 19 June 2023 at 14:12 UTC, a SYN flood targeted a municipal services customer in the Nordics. The attack peaked at 356.0 Gbps and lasted 111 minutes. Traffic originated from 316 autonomous systems in 112 countries, predominantly compromised cloud VMs.
| Vector | SYN flood |
| Peak | 356.0 Gbps |
| Duration | 111 min |
| Time to mitigation | 0.416 s |
| Attack traffic reaching origin | 0.045% |
| Legitimate traffic challenged | 0.37% |
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 17 points of presence.
What the customer saw
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Keep origin IPs out of public DNS history.
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
Is the risk score exposed in the logs so we can build our own dashboards on it?
Thanks! Yes — the risk score and its components are included in every log record.
Thanks — sharing this with our on-call team.