(See the best response by GreatPirateEra.)
I updated Byond today (to version 512.1398), only for my antivirus (Norton) to come up with a message telling me that byond.exe is trying to listen for connections from other computers or something like that and that it is a virus. I tried allowing byond.exe, but Norton still automatically prevented Byond from accessing the Internet. In sum, can anyone help me with this? Is this a real issue? Byond was fine before.
Best response
Norton's the issue.
The pager listening to connections is normal and expected behavior, and it needs to be allowed. Same for Dream Seeker and Dream Daemon.

You need to tell Norton that its detection of the program is a false positive. It would also be helpful to tell the company itself.