Any reason to worry?

For past while now (meaning going on a week), I have been getting a very strange block attempt coming through the IGMP port. I have no idea what this means or what could be causing it so I hope someone can assist me.

I do use ZoneAlarm Free Firewall & Anti-virus, but I also use PeerBlock to keep an eye on any unusual connection attempts.

It is becoming an every minute by minute basis I am getting an IGMP block attempt coming from the DoD Network Information Service (source IP address: based in Ohio) and it’s trying to reach the IP destination

I have learned that the destination IP is multicasting, but it just makes me wonder if it’s worth worrying over the fact I might be spyed on. Whether or not that is the case, I wonder why on earth it’s happening to me.
I have fully re-formatted and installed my computer and this is still happening.
Any advice would be greatly appreciated.
(I’m new here and if this is not in the right section, please move it to the correct section so I can get used to being on this forum)