Their bot notification doesn't give instances and data to support what they see ... they just tell you they've seen traffic, and suspect it ... and when you ask them for the details they never write back assuming that the customer has no clue and should just take comcast at its word..
same company that was found to be lying about their "traffic shaping" for people who were using bit torrent ... not even going after the specific people involved in *over* use .. but just anyone regardless of how much traffic they had consumed.
If your wireless isn't open, and you're using WPA/WPA2 and not with an easy pass-phrase ... you should be relatively ok.. but you should try to monitor usage to see if someone's using your net while you're not there... also try anyway to contact Comcast to ask them if they can get you specific details that lead them to believe the traffic is bot related. You never know, if most of the customers started asking them for proof, maybe then Comcast would send it by default rather than just the "hey we think you're infected" notices, regardless of their belief.
I did get my notice after I'd reinstalled my debian workstation... from downloads ... so it was heavily hitting for about an hour and without any other proof from them, or follow up notices telling me they're still seeing something I'm going on the thought that their script doesn't really know, that they didn't really do what they claimed ... and that they took a short cut in coming to the conclusion I'd be infected..
I do know.. that there are ports open on the 722k that you can get data from it ... but unless your 722k is opening a port with UPnP there shouldn't be any random traffic to it ... and only if you had a Sling Adapter connected would you expect to have an open port through your linksys open to everyone. So could it be hacked ... yes.. but have there been proof of crackers? not that I've seen or heard.. anyone else hearing of it.. do tell and give links for people to follow to learn more..