The Domain Name servers map domain names to IP addresses and back. There are forward and reverse mappings. Both mapping are not necessarily done by the same Name server. If a hacker can alter these mappings, he can masquerade as a trusted client. Server does reverse lookup on 10.10.10.10.
Hackers also try to insert bogus DNS information into legitimate Name servers.
Upgrade to BIND 4.9.3. If TCP sequence numbers are predictable, a hacker can forge a connection from another machine. Thus the server's sequence number is very predictable. This attack was successfully used by Kevin Mitnick to break-in to several Internet machines 14 months ago. Read the book Takedown by Tsuomo Shimomura, one of the victims.