1. A computer method for providing security for intermediate programming code for execution by a virtual machine, the method comprising: receiving ( 200 ) a plurality of bytecode instructions of said intermediate programming code; converting ( 230 , 235 ) said plurality of bytecode instructions, said conversion comprising a step of inserting at least one bytecode instruction relative to a function for execution checking of at least one bytecode instruction of said plurality of bytecode instructions; and generating bytecode, the generated bytecode comprising said plurality of converted bytecode instructions.