On Thursday 27 April 2023 at 14:15 UTC, a UDP reflection (NTP) targeted a retail banking customer in the UK. The attack peaked at 107.2 Gbps and lasted 29 minutes. Traffic originated from 188 autonomous systems in 72 countries, predominantly hijacked home routers.
| Vector | UDP reflection (NTP) |
| Peak | 107.2 Gbps |
| Duration | 29 min |
| Time to mitigation | 0.715 s |
| Attack traffic reaching origin | 0.018% |
| Legitimate traffic challenged | 0.29% |
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 24 points of presence.
What the customer saw
The customer’s status page stayed green throughout; they learned about the attack from our notification.
Recommendations
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
- Keep origin IPs out of public DNS history.
How do you avoid challenging uptime monitors and partners?
Clear and practical, thanks.
Our auditors asked for exactly this kind of incident evidence under DORA.
Great to hear, thanks for sharing your experience.
Would love a follow-up on how you handle HTTP/3 fingerprinting.
Good question. We will cover that in a follow-up post.
The point about origin IPs leaking through certificate transparency logs is underrated.
Machine-readable ranges are at /ips.json and via the API.
Nice to read a vendor blog that admits what went wrong.
Would love a follow-up on how you handle HTTP/3 fingerprinting.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.
Thanks! Yes — the risk score and its components are included in every log record.
Interesting that most attacks are under ten minutes. Our experience is similar.