Technologies for an application reputation service to assist users with minimizing their computerized machines' exposure to and infection from malware, including an application reputation service that contains the reputations for elements (e.g., applications) that are known to be non-malicious as well as those known to be malicious. In one example, when a user attempts to install or execute a new application, the service is queried by the user's machine with a set of identities for the element. The service determines the reputation of the application by referencing a knowledge base of known reputations and returns an indication (e.g., an overall rating, or a flag) of how safe that application would be to install and run on the user's computer.