A system and method prevent malware, spyware and other undesirable applications from affecting mobile communication devices, which use 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 characterization assessment and can also provide a characterization re-assessment for the application, or data object, and transmits the assessment to the device. Performing analysis on a server reduces the battery and performance cost of protection. 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 then perform a characterization re-assessment of a data object it has previously assessed.