Is there any app which can tell which app is using internet?

I have installed lots of apps on my phone. For the last couple of weeks i am facing one issue. Even when i am not using internet infact even when i am not using my phone at all, a window pops up and says you have just downloaded ??mb of data!!! and because of this my battery is draining very fast. I have to charge it twice a day. I don't even know which app is accessing net, I suspected the pulse feed reader and google+ for this. Uninstalled pulse reader but still there is problem. If i could got to know which app is that then i will just uninstall that. Phone: HTC Desire S OS: Android 2.3.3