Strange DNS client behavior

Simon Waters Simon at
Wed Oct 31 01:36:09 UTC 2001

"Aaron M. Scarisbrick" wrote:
> That's just broken.  Why would a single host need hundreds of
> concurrent TCP queries open?  A tcpdump of each of the hosts (tcpdump
> -n -l src x.x.x.x), showed that each host was performing an "ANY?" DNS
> query for the same domain over and over again.  Anybody know of a
> resolver or mailer that opens hundreds of concurrent queries against
> one DNS server for the same query over and over again?  I've resorted
> to using the BIND blackhole access list to prevent the worst abusers
> from pegging the server.  Any light that anyone can shed on this would
> be greatly appreciated.

Maybe your giving back an answer that isn't good - low time to
live, servfail, lameness.

Let us know the domain and nameserver IP and we can start by
ruling out misconfiguration your end.

It could be a DoS attack, as the use of TCP seems unusual, but
it could be that the ANY query returns too much data, without
the domain name we can't tell.

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