Threat Bulletin 0930: Slowloris against a retail banking platform in the Nordics

On Saturday 21 September 2024 at 12:52 UTC, a Slowloris targeted a retail banking customer in the Nordics. The attack peaked at 58.9 million requests per second and lasted 124 minutes. Traffic originated from 1370 autonomous systems in 54 countries, predominantly hijacked home routers.

Vector Slowloris
Peak 58.9 million requests per second
Duration 124 min
Time to mitigation 0.318 s
Attack traffic reaching origin 0.070%
Legitimate traffic challenged 0.55%

Timeline

The attack was preceded by a hacktivist channel announcing the target. Request rates on the targeted routes exceeded their hourly baseline by a factor of 51 within 29 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

The customer’s status page stayed green throughout; they learned about the attack from our notification.

Recommendations

  • Review allow-listed partner ranges quarterly.
  • Keep origin IPs out of public DNS history.
  • Add a dedicated rate limit for the targeted route.

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