Its telling you there is a security vulnerability and implies you should be allowing transfer by hostname rather than IP address.
Also for DNS there is security that allows you to have keys (TSIG or RNDC). I'm still reading up on this myself. A document from 2003 that talks about TSIG and DNS security in general can be found at:
Another document I found later that talks about RNDC (which is what my RedHat came with) is at:
There may be better ones. As noted I haven't finished my reseach.
The above will give you examples of allow-transfer statements in named.conf files so you can see how they should be structured.