is this a DOS attack

[Chris]

In my log file this entry appears at least 50 times in succession..

client 209.87.232.140#1307: update denied: 1Times(s)

Can anyone say if this is a DOS attack? I am running the security measure 
"allow-transfer { none; };
If this was a regular query then why is it happening so often in succession 
and so persistent.  The IP address resloves to 
"dialup-ott-nasi-6.cuic.ca"  If I was to translate, I would say that this 
host is out of Canada, Province of Ottawa maybe an ISP... My primary 
concern is about the DOS question....

Thanks
Chris