Threat Bulletin 1044: cache-busting query flood against a B2B SaaS platform in the UK

On Wednesday 26 February 2025 at 19:49 UTC, a cache-busting query flood targeted a B2B SaaS customer in the UK. The attack peaked at 30.9 million requests per second and lasted 155 minutes. Traffic originated from 807 autonomous systems in 102 countries, predominantly residential proxy networks.

Vector cache-busting query flood
Peak 30.9 million requests per second
Duration 155 min
Time to mitigation 0.860 s
Attack traffic reaching origin 0.041%
Legitimate traffic challenged 0.18%

Timeline

The attack was preceded by a breaking political story. Request rates on the targeted routes exceeded their hourly baseline by a factor of 258 within 31 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

No customer-visible impact. The on-call engineer was notified and acknowledged the incident from the dashboard.

Recommendations

  • Enable log streaming to your SIEM for faster correlation.
  • Keep origin IPs out of public DNS history.
  • Enable authenticated origin pulls.

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