On Saturday 31 July 2021 at 20:31 UTC, a SYN flood targeted a healthcare portal customer in the Benelux. The attack peaked at 269.0 Gbps and lasted 60 minutes. Traffic originated from 2970 autonomous systems in 92 countries, predominantly mobile carrier ranges.
| Vector | SYN flood |
| Peak | 269.0 Gbps |
| Duration | 60 min |
| Time to mitigation | 0.540 s |
| Attack traffic reaching origin | 0.071% |
| Legitimate traffic challenged | 0.75% |
Timeline
The attack was preceded by a ransom note demanding payment in Monero. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 13 points of presence.
What the customer saw
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Add a dedicated rate limit for the targeted route.
- Keep origin IPs out of public DNS history.
- Enable log streaming to your SIEM for faster correlation.