To prevent malware, spyware and other undesirable applications from affecting mobile communication devices (e.g., smartphones, netbooks, and tablets), a device uses a server to assist in identifying and removing undesirable applications. When scanning an application, a device transmits information about the application to a server for analysis. The server receives the information, produces a categorization assessment and can provide a categorization re-assessment, and transmits the assessment to the device. By performing analysis on a server, a device can reduce its battery and performance cost of protecting against undesirable applications. The server transmits notifications to devices that have installed applications that are discovered to be undesirable. The server receives data about applications from many devices, using the combined data to minimize false positives and provide comprehensive protection against known and unknown threats. The server can accumulate this data and perform a categorization re-assessment of a data object previously assessed.