I don't know about now but in the RAAF our log books were checked by the flight commander every month and signed as a true record. A junior officer was first given the task of comparing the log book hours with the squadron flight records then the log book was signed by the flight commander. No way could hours be faked. If mistakes discovered in the log book you were severely bollocked. Bit different in GA where anything goes and personal integrity goes out the window.
Many years ago saw a former Ansett first officers log book where he claimed 2500 hours of instrument flying in 727's in a total of 5000 hours. Cheating? Sure; but it got him a job in Dragonair where he eventually became a very rich captain. Crime sometimes does pay