To your question of is it possible to hack into a computer through winmx the answer is no, of course your computer has other open ports running for things such as microsoft updates and some vendors also keep a port open to check for product updates of installed software, these will always be more easier to a hacker that trying (and failing
) to use the same ports winmx is using while its active.
Any application running on your machine (winmx included) that reaches outside of your machine will use a set of instructions in a certain format, in virtually all cases hackers trying to enter via a machines open ports will be ignored as they are not sending the correct type of instruction that a program recognises, and even if it did its more than likely the program has been "hardened" against internet attacks, its a simple fact that running even a basic firewall will block 99% of unwanted visitors.
I hope your reassured and informed Voyager.