The remote Debian host is missing a security-related update.
Matthew Horsfall of Dyn, Inc. discovered that BIND, a DNS server, is prone to a denial of service vulnerability. A remote attacker could use this flaw to send a specially crafted DNS query to named that, when processed, would cause named to use an excessive amount of memory, or possibly crash.
Upgrade the bind9 packages. For the stable distribution (squeeze), this problem has been fixed in version 1:9.7.3.dfsg-1~squeeze10.