An improved technique involves authenticating a user requesting access to a particular mobile device using knowledge-based authentication (KBA) questions generated from data taken from a group of mobile devices to which the particular mobile device belongs. Along these lines, consider a corporation that has a group of mobile devices distributed to its employees. The mobile devices provide data to an enterprise KBA (eKBA) server regarding events on each of the mobile devices. Because an owner of a mobile device belongs to a group of employees, the owner is able to answer questions regarding fellow employees. On the other hand, a malicious user that illegitimately gains access to the owner's mobile device will not be able to answer such questions, even if the malicious user knows details about the owner.