If it is your program (and not a derivative of somebody else's program, or something that a lot of other people has contributed to), you have the full right to do whatever you like. So just create a new distribution and state that this distro is under "GNU GPL version 3", replace
LICENSE.txt and edit any copyright notices to refer to the correct license - and you're done. Doing so will give you the "additional protection" you believe is offered under the newer version of GPL. Also doing so will not license any future work you do on the program under the GNU GPL version 2.
Of course, the old version will still exist and be licensed under GNU GPL version 2. There is nothing you can do to stop that from being distributed.
Note that doing this will create a fork of your program. GNU GPL version 2 and version 3 are mutually exclusive – so doing this will create all sorts of problems for downstream recipients, and probably confuse a lot of developers unaware of all the pesky intricacies of FLOSS licensing.
So it is IMHO not a good idea to change from one license into another, incompatible license in the middle of a program's life cycle. But if you want to do this, there is nothing to stop you from doing so,