Invalid client message

The hobbitd section reports the following status message:

Latest errormessages:
Invalid client message - blank hostname

Now I would like to see the IP of the server sending this invalid client message to solve the Problem.
In general the IP-Adresses of the senders should be checked by comparing it with a nslookup of the hostname, because it's a security issue when any host can send the reports for another host (It works - I just tried!) which could be damaged without that the HobbitMon notices it...

Thanks an regards

Christian