There is a person on another forum I went to who seems to have spent 2 weeks figuring out the viruses and hacked them onto pokemon (or just hacked the pokemon with the virus in, I'm not sure which) then traded those pokemon and destroyed a few people's save files (and made it so illegal pokemon show up everywhere on others (including some that don't exist)) before he was caught and banned. He never posted his friend code (all his trades were done through PMs) and his username was a series of numbers. (the forums didn't have a character limit on the usernames because the person who programmed it (it was a custom programmed forum) forgot to put one in, and the username filled up the entire screen and that itself almost crashed the forums. It was a really bad and small forum and 3 weeks ago it did crash, and I don't even remember the name or URL of it now) Be aware of that person, my friend's game file wasn't destroyed, but his game got so corrupted that he found a level 200 "death" (one of the nonexistent pokemon that the virus caused) in a pokemon center, and when he tried to run, he threw a masterball and caught it, which caused the game to go completely berserk, and changed the maps around so the land routs actually formed words (die) then the screen went black and whenever my friend tries to load the game, the DS crashes. As far as I know the only reason he hasn't become famous for hacking is because he destroyed his own game accidentally. Therefore, he shouldn't be a threat to us, but if he has $35, he could buy a new game. (he actually was never seen again, the only reason I know his game crashed was because it was his last post on the forums before he was banned.)
Most of the things he did I didn't know was possible. (although I did see it happen to my friend's game, I saw the trade, and what happened next)