San Francisco-based cybersecurity startup Abnormal Security announced that it has raised $250 million in a Series D funding round, bringing its total funding to $546 million and its valuation to $5.1 billion. The funds will be used to expand its AI-based cybersecurity platform, accelerate global growth, and boost product investment, particularly enhancing its AI decision-making capabilities. Abnormal Security focuses on providing AI-driven security solutions to help enterprises and organizations defend against various email attacks.