Disclosed is a system for recommending content of a predefined category to an account holder, detecting spam applications, or account holders based on the account holder application graphs. The system receives information corresponding to applications executing on the client device of the account holders and generates an application graph for each account holder that includes a list of predefined application categories that are preferred by the account holder. For each predefined category, a list of account holders preferring content relevant to that category is predicted based on the set of generated application graphs. Some application graphs may be detected as spam application graphs by comparing the generated application graphs with a set of predefined spam application graphs. Alternatively, if the generated application graph does not match the predefined spam application graphs, they are compared to a set of application graphs from a database to find similar application graphs.