User behavior data of multiple users is acquired, and multiple user eigenvalues of user behavior data of each user under preset multiple user behavior dimensions are extracted. A user eigenvector of each user is determined based on the multiple eigenvalues of this user. Multiple user classes are obtained by clustering the user eigenvectors of multiple users are clustered through a preset clustering algorithm. A central vector of each user class is determined based on the user eigenvectors included in this user class. A difference eigenvector of each user class is determined, wherein a distance between the difference eigenvector and a central vector of an aggregation class to which the difference eigenvector belongs is not within a preset distance range. A user characterized by the difference eigenvector is determined as an abnormal user.