Mature members of the Billion Dollar Startup Club are seizing on investor excitement surrounding initial public offerings by big tech startups.

In one of the latest signs, Carbon Black Inc., which was founded 16 years ago, on Monday disclosed its own IPO plans, more than 18 months after WSJ Pro Venture Capital reported it had confidentially filed. That filing comes as some of the grayer unicorns are pouncing on investor appetite for cybersecurity exposure in the wake of high-profile breaches of giant corporate networks.

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