ABMNet is a private gnet. A number of USENET newsgroups have members forming their own private subnets for making files available. ABMNet sounds like one of the ones from alt.binaries.multimedia.* pantheon. The connection data for that is actually semi-public (public but don't post it in a webforum or send it to someone who is a prig).

For those wondering, generally, the admission fee for private subnets is that the person posts some files to the newsgroup or is a friend of someone that already has access. In such ways, the USENET newsgroups and IRC serve as subnet recruitment sources for new subnet members.

One of the values of subnets lies in not having a rogue member post the connection data to other people at random such as people who have never posted files to the newsgroup. Generally, this is because the people who "work" for their access by posting files have the greatest respect for those other members of the subnet. I have seen this in effect in several subnets already and it is refreshing.