Original URL: http://www.theregister.co.uk/2009/10/13/sweden_dns_outage/

Missing dot sends Sweden tumbling off internet

DNS doldrums for mournful Scandies

By John Oates

Posted in Networks, 13th October 2009 17:31 GMT

Sweden effectively fell off the internet last night when maintenance to Domain Name Systems damaged every single .se web address.

The problem happened at quarter to ten last night and took just less than an hour to fix.

But some problems remained because the address data is cached externally by ISPs - these servers had to be flushed - some ISPs outside Sweden, unaware of the problem, may still be having problems finding addresses ending in .se.

An error in a script used to update the .se domain led to an error being introduced into every single domain name. The software failed to add the fullstop to .se addresses. This meant the system failed to understand that .se was the top level domain.

According to pingdom - the Swedish company which monitors websites' uptime - the problem was made worse because the duff data was then cached by external ISPs.

Pingdom said it was not uncommon for individual sites to have DNS problems, but far more unusual for an entire country to get wiped out. It said the effects were serious in Sweden, with 900,000 .se addresses, but would have been far worse if the 80 million .com addresses had been corrupted.

The Swedish registry, the Internet Infrastructure Foundation, said the problem was caused by an incorrect zone file used during planned maintenance. The firm's testing procedures did not pick this up, but its surveillance system did once the software was in use.

Once this happened a new zone file was created and distributed within an hour. The Internet Infrastructure Foundation said ISPs still having trouble should flush or restart machines. There's more advice here.

IIF is investigating to see if its internal procedures need to be improved. ®