Threat Bulletin 0447: TLS handshake exhaustion against a tax authority portal platform in Southeast Asia

On Tuesday 8 November 2022 at 21:35 UTC, a TLS handshake exhaustion targeted a tax authority portal customer in Southeast Asia. The attack peaked at 644.0 million requests per second and lasted 189 minutes. Traffic originated from 2794 autonomous systems in 113 countries, predominantly a rented booter service.

Vector TLS handshake exhaustion
Peak 644.0 million requests per second
Duration 189 min
Time to mitigation 0.151 s
Attack traffic reaching origin 0.049%
Legitimate traffic challenged 0.03%

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 537 within 37 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

  • Keep origin IPs out of public DNS history.
  • Enable log streaming to your SIEM for faster correlation.
  • Review allow-listed partner ranges quarterly.

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