Abstract: A computer-implemented method obtains information about an external computer system having a connection to a computer system. The method may comprise receiving a request from the external computer system. In response to categorizing the external computer system as a potential threat responsive to the request, a computer file is generated responsive to the request. The computer file comprises instructions which are designed for obtaining the information about the external computer system if the instructions are executed on a processor of the external computer system. Furthermore, data is provided responsive to the request. The data is sent together with the computer file to the external computer system. The information about the external computer system, which is generated responsive to the instructions of the computer file, is received by the computer system for preserving it for a later use for developing measures for protecting the computer system.