How is this possible?

Hello everyone.

I'll get straight to the point. Every day or so I play a game. I also have a lot of my friends that play this game. My friends and I all live within 5 miles of each other.

Recently (within 2 months of so), every one of my friends were hacked on the game simultaneously. This is event baffled all of us, especially me because I am the most tech savvy of them all and I knew that they were not the kind of people that would click on random links and download viruses. Well, we thought it was the end of it.

Now, today, I was talking to my friend on Skype and he says that he was hacked again. My friend recovers the password and we thought it was the end of it, again. I then go and take a shower. As I return to my computer within 15 minutes of leaving it, my friend calls me again. He said that he was hacked AGAIN, even though he changed his password 15 minutes ago. Then, I go on and I found out that I was hacked as well! Also, another one of my friends was hacked twice within this week.

Now what I don't understand is that the game has a Bank PIN system, a series of buttons you have to press on a screen ( so it cannot be keylogged ) to gain access to one's bank within the game. When we were all hacked, our banks were accessed. This means that somebody must have known our game bank PINs, even though they are impossible to key log.

Perhaps the craziest part of this is that: we all get hacked at the same time (within 30 minutes, three people) and we do not download viruses / accept phish emails / download things from instant messenger conversations / etc.

How is this possible? How do three people get hacked on a game within 30 minutes multiple times, especially when none of us tend to download any viruses/keyloggers/malware. I scanned my computer three times (after the hack) with three different anti-virus programs - no problems came up.

I am the only one using a Macintosh out of my friends.
Can any of you guys provide input upon this issue?
My brother suggests that I should just reinstall the OS, but I doubt it'll work.

Thanks a ton in advance guys!

 

The game is RuneScape. Hacked as in the contents of your game account are gone. As far as I can tell, no other personal information was stolen (e-mail accounts, etc) - so it was only the game.