IBM Tuesday announced its intent to acquire vulnerability-assessment security firm Watchfire for an undisclosed price.

IBM expects the acquisition to be completed by the third quarter of this year, subject to regulatory review, and that Watchfire, which has 189 employees, will continue to operate as an independent business unit.

Watchfire markets a Web application security tool called AppScan, which will be added to the IBM Rational software line as a security, compliance and quality-testing tool.

Privately held Watchfire, founded in 1996, is said to have more than 800 customers. IBM has been actively acquiring security firms during the past year, including Internet Security Systems, Consul and Micromuse, to broaden its product portfolio as it maps out its service strategy for IT risk management and compliance.