San Francisco-based MarkMonitor, which develops online brand protection services and technology, has been acquired by Thomson Reuters, the publisher said Thursday. Financial terms of the acquisition were not announced. MarkMonitor becomes part of Thomson Reuters' Intellectual Property & Science business. Thomson Reuters said that the buy adds more than 400 employees from MarkMonitor. MarkMonitor was venture backed by Polaris Ventures, Institutional Venture Partners, Cargill Ventures, Foundation Capital, and Focus Ventures.