On Saturday 18 September 2021 at 14:42 UTC, a ACK flood targeted a tax authority portal customer in the Middle East. The attack peaked at 137.3 Gbps and lasted 118 minutes. Traffic originated from 3813 autonomous systems in 111 countries, predominantly a headless-browser farm.
| Vector | ACK flood |
| Peak | 137.3 Gbps |
| Duration | 118 min |
| Time to mitigation | 0.812 s |
| Attack traffic reaching origin | 0.023% |
| Legitimate traffic challenged | 0.33% |
Timeline
The attack was preceded by no stated motive. Edge packet filters identified the flood by source port and payload signature and dropped it at line rate across 18 points of presence.
What the customer saw
A brief increase in p99 latency of 109 ms during the first minute, then normal service.
Recommendations
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable authenticated origin pulls.
- Enable log streaming to your SIEM for faster correlation.