The prohibited program message is also known to trigger in mobiles which are rooted or Maple M Mesos. If your phone is second hand and you are unaware of its own background, this could possibly be the case, as well.
As a last fix, try reinstalling MapleStory M and relaunching it with no other programs running, even ones which are entirely unrelated to hacking. You may have an innocuous app that's somehow triggering the warning.
Failing all this, your best bet is to get in contact with Nexon right and report your issue. As MapleStory M is recently launched on cellular, it's bound to get some hiccups here and there, and the best method to keep this from occurring would be to inform the programmers quickly and politely.
If you are going to take on all of the enemies and obstacles that'll get on your way on your experience in MapleStory M, you will have to have some decent gear on you. We are not only talking about the things you put your hands on at the beginning of the match, but you'll have to keep updating and getting better equipment in order to accept the tougher tests in MapleStory M.
In order to get equipment in MapleStory M, you're going to need to open plenty of treasure boxes. You will get one of buy Maple M Mesos these for free each day you log-in, or you can spend 50,000 Meso to buy one. Alternately, treasure boxes can be seen in the match's Elite Dungeons, in case you feel confident about carrying them on.