[cobalt-security] DNS denied update from external IP address

[johnm@xxxxxxxxxxxxxxxxxxxx]

Please forgive me if htis is a "silly question" but I can't find the 
answer on the list or in any of my books.

I have a Raq4i and have several domains on it.  Recently I have started to 
get the following reported in my log files :-

Dec 18 22:29:52 ns named[394]: denied update from [64.216.13.133].1430 for 
"xxxxx.com"
Dec 18 22:34:54 ns named[394]: denied update from [64.216.13.133].1459 for 
"xxxxx.com"
Dec 18 22:44:55 ns named[394]: denied update from [64.216.13.133].1478 for 
"xxxxx.com"
Dec 18 23:44:56 ns named[394]: denied update from [64.216.13.133].1607 for 
"xxxxx.com"
Dec 18 23:49:57 ns named[394]: denied update from [64.216.13.133].1632 for 
"xxxxx.com"
Dec 18 23:59:58 ns named[394]: denied update from [64.216.13.133].1660 for 
"xxxxx.com"
Dec 19 00:59:59 ns named[394]: denied update from [64.216.13.133].1792 for 
"xxxxx.com"
Dec 19 01:05:01 ns named[394]: denied update from [64.216.13.133].1805 for 
"xxxxx.com"
Dec 19 01:15:02 ns named[394]: denied update from [64.216.13.133].1834 for 
"xxxxx.com"
Dec 19 01:54:27 ns named[394]: denied update from [64.216.13.133].1049 for 
"xxxxx.com"
Dec 19 02:03:25 ns named[394]: denied update from [64.216.13.133].1036 for 
"xxxxx.com"
Dec 19 02:15:03 ns named[394]: denied update from [64.216.13.133].1967 for 
"xxxxx.com"
Dec 19 02:20:04 ns named[394]: denied update from [64.216.13.133].1979 for 
"xxxxx.com"

Should I be concerned (the domain is one of mine and is under my control) 
?  If I should is there anyway to "lock out" this IP address ?

Regards

John