spamming problem

with the recent spamming that has been going on,do you think it would be a good idea to make it impossible to start a thread unless you have at least 5 posts. do you think this will help? ive noticed they sign up, start a thread and leave,at least this will be a pain for them.
is this possible to do

they need to do one of those little things where u gotta enter the number u see when u sign up, that'd stop