On Monday 17 June 2024 at 19:13 UTC, a HTTP GET flood targeted a retail banking customer in the UK. The attack peaked at 417.7 million requests per second and lasted 105 minutes. Traffic originated from 910 autonomous systems in 69 countries, predominantly a headless-browser farm.
| Vector | HTTP GET flood |
| Peak | 417.7 million requests per second |
| Duration | 105 min |
| Time to mitigation | 0.730 s |
| Attack traffic reaching origin | 0.009% |
| Legitimate traffic challenged | 0.70% |
Timeline
The attack was preceded by a publicly announced sales event. Request rates on the targeted routes exceeded their hourly baseline by a factor of 283 within 10 seconds. The risk score of participating clients crossed the challenge threshold automatically and proof-of-work difficulty rose with origin load.
What the customer saw
Checkout conversion was unchanged compared with the same hour of the previous week.
Recommendations
- Lower challenge thresholds on authentication endpoints during high-risk events.
- Enable log streaming to your SIEM for faster correlation.
- Review allow-listed partner ranges quarterly.
How do you avoid challenging uptime monitors and partners?
Nice to read a vendor blog that admits what went wrong.
Do you publish the edge IP ranges in a machine-readable format?
Great to hear, thanks for sharing your experience.
Clear and practical, thanks.
Solid runbook advice. The DNS-at-2am point hit home.
We moved from a scrubbing provider to always-on last year; time to mitigation went from minutes to basically nothing.
We had the exact false-positive issue with CGNAT carriers. The weighting change makes sense.