For cars, there are mechanics. For corporate data breaches, there are Chris Cwalina and Steve Roosa. Cwalina and Roosa are attorneys who lead the data privacy and security team at law firm Holland & Knight, and they are building a novel practice in the world of Big Law. They have created a “lab” to research and test the mobile apps and Web sites of their clients — banks, communications companies and other corporations — to detect security lapses that may enable advertisers or other third-party entities to access consumers’ personal information without them knowing.