A computer system includes a data network connection, a reading device, an input component and a security device, wherein the security device establishes a data network link via the data network connection as the computer system is starting up and said security device further receives access data either via the data network link or via the reading device and the input component, and said security device compares the received access data with a data record stored in a firmware on a memory element and boots the computer system if the comparison was successful.