If the script that updates your DNS records for a zone leaves off the trailing period for each record, the DNS server can't properly attach the top-level domain name. That little tip is probably permanently etched onto the head of an administrator somewhere at Sweden's Internet Infrastructure Foundation. Late yesterday evening, that single omitted period caused Web sites with Sweden's .se TLD to be inaccessible for at least one hour, with some perhaps remaining inaccessible until the following evening before downstream routers refresh their caches.

A security bulletin issued by the Foundation this morning advises administrators noticing difficulties with accessing .se sites to use BIND 9.2.0's rndc flush command to clear memory of cached data prior to a reload. The firm issued a new zone file shortly after the incident, although it admitted it refrained from going through the usual security steps to clear the zone file since .se sites remained inaccessible. A new, fully cleared zone file has since been issued.

Some ISPs, a spokesperson for the .SE foundation told Sweden's English-language daily The Local, may take two days or longer to fix the issue on their sides of the Internet. Larger ISPs such as TeliaSonera and Bredbandsbolaget report having already instituted the fix.

Evidently the problem did not impact copyright violation powerhouse The Pirate Bay, whose .se domain name defaults to its principal Web site with a .org TLD.