Too Many CNAME requests

[Edsonet]

In the past week, I have suddenly started receiving excessive CNAME
requests for our domain name. The requesting server simply ignores the
answer that there are no CNAMES. When the requests reach more than 20 per
second, the requesting server ends up being blocked from our server.

What's is happening all of a sudden?

J.A. Coutts
Systems Engineer
Edsonet/TravPro
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20/09/11
11:07:33   Request from 199.117.52.11 for CNAME-record for yellowhead.com.
11:07:33   Sending reply to 199.117.52.11 about CNAME-record for
yellowhead.com.:
11:07:33   -> Answer: There are no CNAME-Records for yellowhead.com.
11:07:33   -> Authority: SOA-record for yellowhead.com. =
server1.yellowhead.com. (Serial 2000031302)
11:07:33   IP address 199.117.52.11 blocked (more than 20 Requests per second)
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20/09/12
11:25:43   Request from 199.117.52.11 for CNAME-record for yellowhead.com.
11:25:43   Sending reply to 199.117.52.11 about CNAME-record for
yellowhead.com.:
11:25:43   -> Answer: There are no CNAME-Records for yellowhead.com.
11:25:43   -> Authority: SOA-record for yellowhead.com. =
server1.yellowhead.com. (Serial 2000031302)
11:25:43   IP address 199.117.52.11 blocked (more than 20 Requests per second)
------------------------------------------------------
20/09/13
17:48:25   Request from 208.248.127.232 for CNAME-record for yellowhead.com.
17:48:25   Sending reply to 208.248.127.232 about CNAME-record for
yellowhead.com.:
17:48:25   -> Answer: There are no CNAME-Records for yellowhead.com.
17:48:25   -> Authority: SOA-record for yellowhead.com. =
server1.yellowhead.com. (Serial 2000031302)
17:48:26   IP address 208.248.127.232 blocked (more than 20 Requests per
second)
17:48:26   Request from 208.248.127.232 on Block list. Ignored!

18:41:13   Request from 141.202.248.31 for CNAME-record for yellowhead.com.
18:41:13   Sending reply to 141.202.248.31 about CNAME-record for
yellowhead.com.:
18:41:13   -> Answer: There are no CNAME-Records for yellowhead.com.
18:41:13   -> Authority: SOA-record for yellowhead.com. =
server1.yellowhead.com. (Serial 2000031302)
18:41:13   IP address 141.202.248.31 blocked (more than 20 Requests per
second)
------------------------------------------------------
20/09/14
16:29:05   Request from 199.117.52.11 for CNAME-record for yellowhead.com.
16:29:05   Sending reply to 199.117.52.11 about CNAME-record for
yellowhead.com.:
16:29:05   -> Answer: There are no CNAME-Records for yellowhead.com.
16:29:05   -> Authority: SOA-record for yellowhead.com. =
server1.yellowhead.com. (Serial 2000031302)
16:29:05   IP address 199.117.52.11 blocked (more than 20 Requests per second)
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