Most people bring their cameras to the game. You don't have to hide either from the security, they wont to anything if they see you taking pictures.
I think that the rule is that no cameras are allowed. However, if you don't embarrass the usher in that section where you are; you can take pics before, during intermission and after the game.
The above simply means that you shouldn't be taking pictures during the game and that includes time outs.
We three Habs fans from Chicago visited in March 2006 and just as I said above, one of us took pics before, during intermissions and after the game with no trouble. We sat in the Reds in separate seats/rows in the same section, tickets are hard to get and we ordered in November of the previous year] and when the game was over, asked an usher to take a pic of us with the ice in the background and it wasn't a problem.
So, don't push disobeying the rule and you should be okay.
You can always take the camera with you and talk to the usher in your section and have him/her tell you that despite the rule, there are times when you can take pics and you want to know those time periods.