Firewall Reporting Random Files trying to access the internet

Hi.  My Norton Firewall, running on iMac 2010 under OSX 10.8 has started reporting some unusual files trying to access the internet including a .tif file from my aperture folders, various folders and a plist or two.  This seems very odd to me and i wondered if it meant they have been infected.   I have scanned one of them and Norton AV found nothing.  Am I worrying unneccessarily ?   Thanks in advance.


Andy