To securely transmit data from a communication terminal (TC) to an application server (SA) over a telecommunications network (RT), the communication terminal (TC) being connected to the application server (SA) via an unsecure access network (RAns) and being able to communicate with the application server (SA) via at least one secure access network (RAs), the communication terminal (TC) switches the connection with the application server (SA) from the unsecure access network (RAns) to a secure access network (RAs), when personal data (DonP) is likely to be entered or is entered by the user, transmits the personal data (DonP) to the application server (SA) via the secure access network (RAs), and switches the connection with the application server (SA) from the secure access network (RAs) to an unsecure access network (RAns).