What is prisoner.iana.org?

IANA was the name of the organization that was responsible for handing out IP address blocks back in the day.

There was a need for a placeholder zone for the three blocks of non-routable addresses, so IANA setup three DNS servers: blackhole-1.iana.org, blackhole-2.iana.org and prisoner.iana.org.

If a system with the address range: 192.168.XXX.XXX tries to register its PTR record without a local DNS server, it will try to register with prisoner.iana.org. Obviously prisoner.iana.org will reject the request. Hence the many instances of this address in the DNS logs / Event Viewer.