don't worry, 224.* is multicast address, 224.0.0.2 is used to address all routers on your subnet. you machine, or someone on your subnet is trying to use multicast. usually your machine should filter out packets for this address unless you configure your machine as a router, or you have put your interface in promiscous mode. it is okay if you don't know what i am talking about, you only need to know that basically your machien is okay, not being hacked.