A method for addressing, authentication and secure data storage in computer systems comprising at least one first, at least one second and/or at least one third computer system (1a1, 1a2, 1b) with at least one network interface and at least one telephony interface and at least one storage space for administrative information, in particular for at least one authorized call number and/or at least one subscriber PIN in such a way that the computer systems (1a1, 1a2, 1b) are programmed with a program reproducing a control logic for controlling the interaction of the aforementioned interfaces, wherein the method comprises the following steps: a) transmitting the connection information for the network interface of at least one first computer system (1a1) via the telephony interface to at least one second and/or third computer system (1a2, 1b); b) automatically checking a call number of the first computer system (1a1) with the call numbers stored in the storage space in the second or third computer system (1a2, 1b) and, if the outcome of the check is positive, automatically transmitting the connection information for the network interface of the second and/or third computer system (1a2, 1b) via the telephony interface to the first computer system (1a1) and activating the network interface of the second and/or third computer system (1a2, 1b), in order to accept connections on the basis of the connection information of the first computer system (1a1); c) checking the call number of the second and/or third computer system (1a2, 1b) with the call numbers stored in the storage space in the first computer system (1a1) and, if the outcome of the check is positive, activating the network interface of the first computer system (1a1), in order to establish a connection (101, 102, 103, 104) on the basis of the connection information of the second and/or third computer system (1a2, 1b); d) only allowing connections with the connection information of the first computer system (1a1) by the network interface of the second and/or third computer system (1a2, 1b), and e) only allowing connections with the connection information of the second and/or third computer system (1a2, 1b) by the network interface of the first computer system (1a1), and wherein f) the network interfaces of the first and second and/or third computer system (1a1, 1a2, 1b) only allow connection attempts, in particular for between 1 and 10, preferably between 2 and 7, in particular preferably between 3 and 5 seconds, with the respective connection information, and after the connection is established or after the predetermined time period has elapsed without a connection being established these network interfaces are not recognizable or reachable for other computer systems. a) transmitting the connection information for the network interface of at least one first computer system (1a1) via the telephony interface to at least one second and/or third computer system (1a2, 1b); b) automatically checking a call number of the first computer system (1a1) with the call numbers stored in the storage space in the second or third computer system (1a2, 1b) and, if the outcome of the check is positive, automatically transmitting the connection information for the network interface of the second and/or third computer system (1a2, 1b) via the telephony interface to the first computer system (1a1) and activating the network interface of the second and/or third computer system (1a2, 1b), in order to accept connections on the basis of the connection information of the first computer system (1a1); c) checking the call number of the second and/or third computer system (1a2, 1b) with the call numbers stored in the storage space in the first computer system (1a1) and, if the outcome of the check is positive, activating the network interface of the first computer system (1a1), in order to establish a connection (101, 102, 103, 104) on the basis of the connection information of the second and/or third computer system (1a2, 1b); d) only allowing connections with the connection information of the first computer system (1a1) by the network interface of the second and/or third computer system (1a2, 1b), and e) only allowing connections with the connection information of the second and/or third computer system (1a2, 1b) by the network interface of the first computer system (1a1), and wherein f) the network interfaces of the first and second and/or third computer system (1a1, 1a2, 1b) only allow connection attempts, in particular for between 1 and 10, preferably between 2 and 7, in particular preferably between 3 and 5 seconds, with the respective connection information, and after the connection is established or after the predetermined time period has elapsed without a connection being established these network interfaces are not recognizable or reachable for other computer systems.