"All they need is one person to click on it, and then they go from there," he said, referring to hackers. "That's why false negatives are pretty dangerous."
Abnormal Security is considerably larger than Material and Sublime, with over $200 million in annualized revenue. It's quickly gaining market share, according to Peter Firstbrook, vice president and distinguished analyst at industry researcher Gartner.
Some companies use Abnormal Security as an add-on to Mimecast or Proofpoint, he said. For years, businesses have called in Proofpoint to filter messages before sending them along to Microsoft-based inboxes, he said, adding that Proofpoint's year-over-year revenue growth rate is now in the teens after being in the thirties as recently as 2018.