Microsoft is acquiring Aorato, an Israel-based security vendor, for about $200 million in a move to beef up security of Active Directory.

The acquisition isn't a big surprise. It was announced that Microsoft was looking at buying Aorato back in July, but Microsoft has not made any official announcements regarding the terms of the deal.

"I'm pleased to announce today that Microsoft has acquired Aorato, an innovator in enterprise security," said Takeshi Numoto, corporate VP of cloud and enterprise marketing at Microsoft. "We are making this acquisition to give customers a new level of protection against threats through better visibility into their identity infrastructure.  With Aorato we will accelerate our ability to give customers powerful identity and access solutions that span on-premises and the cloud, which is central to our overall hybrid cloud strategy."

Aorato essentially provides "intelligent" protection inside a company's networks by learning what behavior is normal and what isn't. When it detects abnormalities it takes action.

The information that it learns is based on a continuously updated "security graph," which is able to map out every user and device using Active Directory. Active Directory is a tool used by businesses for user access credentials to systems and applications.

Aorato first got Microsoft's attention when it detailed an Active Directory security vulnerability in a blog post written by one of its executives. At the time of the post, Microsoft heavily downplayed the concerns that were raised.

Aorato recently closed a round of funding that raised $10 million and was led by Accel Partners and Innovation Endeavors. A number of other investors were involved in the funding, including Israel-based company Glilot Capital venture fund as well as the two founders of Trusteer, an information-security company based in Israel that was bought by IBM in 2013 for $650 million.

Aorato was founded by veterans of the Israeli defense force and has raised a total of $11 million in funding.

"We are excited about the technology that Aorato has built and, especially, the people joining the Microsoft team through this acquisition. In the mobile-first, cloud-first era, Microsoft is committed to moving nimbly and aggressively to provide customers with solutions to their top challenges," continued Numoto in his blog post.