To attack a z/OS system via a network connection, it is often not necessary to have any special knowledge of z/OS or the network architecture at hand. Due to their TCP/IP connections to (in some circumstances public) networks and Unix System Services, many z/OS systems can be reached by external attackers using standard protocols and services such as HTTP or FTP. External attackers can, in certain circumstances, carry out denial-of-service attacks against the services provided over a TCP/IP connection to public networks, or read or tamper with transmitted data without authorisation. Internal attackers can try to increase their authorisations using a TCP/IP connection to internal networks by obtaining the ID and password of a user with SPECIAL rights (for instance).