Microsoft said it has acquired Komoku, a small, veteran-owned security software firm that specializes in anti-rootkit products.

Financial terms of the deal, disclosed last week, were not announced.

Microsoft said it plans to add Columbia, MD-based Komoku's offerings to its Forefront line of enterprise security products, and to its Windows Live OneCare service for home users.

Komoku was founded in 2004 by William Arbaugh, a former Army officer and National Security Agency official. The company's products are designed to eliminate from computers so-called rootkits -- malicious bits of software that often thwart detection by standard antivirus programs by invading a PC at the administrator level.

Rootkits entered the broader public lexicon in 2005 when Sony BMG infamously placed such malware on its Windows-compatible music CDs. The company claimed the move was aimed at enhancing copy protection, but eventually apologized.

Komoku's customers include the Department of Homeland Security and the Department of Defense. Microsoft security division general manager Ryan Hamlin said in a statement that it was Komoku's work for "ultra security-conscious customers" that in part attracted his company to the deal.

Once shy about acquisitions, Microsoft has been on somewhat of a buying binge over the past couple of years. Komoku represents the company's seventh announced buyout this year. In January, Microsoft announced a $1.2 billion bid for Norwegian enterprise search engine company Fast Search and Transfer.

In February, Microsoft stunned the markets with the disclosure of an offer to acquire Internet rival Yahoo for $44.6 billion. Yahoo has to date rejected the offer.

Microsoft's buying binge appears to be coincident with the company's appointment of Christopher Liddell as chief financial officer in 2005.

The company has announced 55 transactions from 2005 through the present. By contrast, Microsoft announced only 12 deals over the three years prior to Liddell's arrival. Liddell, a New Zealand native, joined Microsoft in May of 2005 from International Paper, where he was also CFO.