An Internet service provider uses virtual machines dedicated to one (or a few) customers to perform transactions on behalf of those customers, where the transactions require sensitive or confidential user authentication data. Each virtual machine only has access to the user authentication data it needs to perform the transactions for its dedicated customers, not authentication data for all the customers of the service provider. Virtual machines are shut clown when not performing transactions or interacting with customers, thus further reducing the risk of disclosure of the confidential user authentication data.