On Sunday 1 May 2022 at 17:01 UTC, a Slowloris targeted a developer platform customer in Iberia. The attack peaked at 898.0 million requests per second and lasted 67 minutes. Traffic originated from 219 autonomous systems in 108 countries, predominantly a Mirai-derived IoT botnet.
| Vector | Slowloris |
| Peak | 898.0 million requests per second |
| Duration | 67 min |
| Time to mitigation | 0.219 s |
| Attack traffic reaching origin | 0.009% |
| Legitimate traffic challenged | 0.50% |
Timeline
The attack was preceded by a ransom note demanding payment in Monero. Request rates on the targeted routes exceeded their hourly baseline by a factor of 411 within 32 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
A brief increase in p99 latency of 219 ms during the first minute, then normal service.
Recommendations
- Add a dedicated rate limit for the targeted route.
- Review allow-listed partner ranges quarterly.
- Enable log streaming to your SIEM for faster correlation.
Interesting that most attacks are under ten minutes. Our experience is similar.
Nice to read a vendor blog that admits what went wrong.
Solid runbook advice. The DNS-at-2am point hit home.