Which home use antivirus, freeware, or shareware, and by home use I mean not Sophos enterprise, has the most open ports? In particular which leaves 3 open ports for Realplayer?
Try running 'shields-up' online port scan and see what your router is broadcasting to the world. https://www.grc.com/shieldsup
@dnewhous umm, i really don't think that your av is the culprit here.look elsewhere like a misconfigured router or fw you know.
hardware firewalls are robust. Any one with a broadband modem/router already has one enabled by default.
I know there was a spate of ISP's supplying routers with the SPI firewall disabled by default, Virgin Media here in UK were one such culprit.
"it ain't necessarily so..." (Gershwin Bros, Porgy & Bess) Routers supply NAT which acts an effective Stateless Firewall, but only some have SPI, see http://whirlpool.net.au/wiki/hw_feature_118.