Is there a list of active Monero full nodes?
Something like Bitnodes for Bitcoin that maintains a list of IP addresses for currently active Monero nodes.
Nodes are aware of the nodes that they are connected to and can request a list of peers from those nodes. These lists can identify a many nodes, but a significant number will always be missed. Some nodes are only online part time, may have closed ports, or frequently change IP addresses, making accurate tracking more difficult. Monero Hash attempts to track Monero nodes but is not aware of all of them as explained by Riccardo Spagni in a recent interview on Bitcoin Uncensored:
Monero Hash tracks nodes, but they don't track every single node. Its not like they are plowing through nodes like chain analysis would, trying to enumerate them. As an example they track 1 node in South Africa, but I am running two and I know two other people that are running full nodes here. So the fact that are only tracking one South African node means they are not tracking everything. They are tracking like 400+ full time nodes that are instantly accessible with open ports. Probably 2-3 months ago we were sitting on 100-125 nodes.