On Monday 27 September 2021 at 11:09 UTC, a SYN flood targeted a B2B SaaS customer in the Benelux. The attack peaked at 106.1 Gbps and lasted 45 minutes. Traffic originated from 4150 autonomous systems in 12 countries, predominantly mobile carrier ranges.
| Vector | SYN flood |
| Peak | 106.1 Gbps |
| Duration | 45 min |
| Time to mitigation | 0.755 s |
| Attack traffic reaching origin | 0.015% |
| Legitimate traffic challenged | 0.34% |
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 22 points of presence.
What the customer saw
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Enable authenticated origin pulls.
- Keep origin IPs out of public DNS history.
- Lower challenge thresholds on authentication endpoints during high-risk events.