hello

i want to know how to monitor my users Personal messages ... because i am an administrator of a forum that it's users are my students ... and i want to control there behavior ... and lately i noticed that there are some of them use the personal message including links that allow them to hack another user or links of sex sites

and at the same time i don't want to disable the Personal messages ..

i need help ... thanks for reading .. waiting for help

regards,
asa