Horizon3 raised $250 million in a Series E funding round to continue growing its NodeZero platform that uses artificial intelligence to defend against AI-driven cyberattacks. We started with pentesting, evolved to be a proactive security platform, and will now accelerate remediation by creating AI learning loops between attackers and defenders.” Pentesting, or penetration testing, is a cybersecurity technique in which ethical hackers use the tactics of the most sophisticated adversaries to discover and fix security vulnerabilities before they can be exploited. Horizon3’s Series E funding round was co-led by NightDragon and NEA. NightDragon Founder and CEO Dave DeWalt said in the release that Horizon3 “coined the concept of cyber warfare being AI vs. AI, and that future has arrived.”