1. A computer security method comprising: loading ( 200 ) a software application ( 100 ) from a non-volatile memory ( 101 ) into a volatile memory ( 102 ) of a computer system ( 104 ), performing a first authentication ( 202 ) of the software application, starting execution ( 204 ) of the software application after the first authentication, and performing a second authentication ( 206 ) of the software application during the execution.