On Thursday 12 August 2021 at 23:09 UTC, a SYN flood targeted a education platform customer in the UK. The attack peaked at 124.5 Gbps and lasted 188 minutes. Traffic originated from 1633 autonomous systems in 38 countries, predominantly compromised cloud VMs.
| Vector | SYN flood |
| Peak | 124.5 Gbps |
| Duration | 188 min |
| Time to mitigation | 0.742 s |
| Attack traffic reaching origin | 0.069% |
| Legitimate traffic challenged | 0.12% |
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 33 points of presence.
What the customer saw
A brief increase in p99 latency of 83 ms during the first minute, then normal service.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Enable authenticated origin pulls.
- Lower challenge thresholds on authentication endpoints during high-risk events.
The point about origin IPs leaking through certificate transparency logs is underrated.
Great write-up. We saw almost the same pattern on our login endpoint last month.
Any plans to support per-tenant limits keyed on a JWT claim?
Do you publish the edge IP ranges in a machine-readable format?
How do you avoid challenging uptime monitors and partners?