Last night (12 October 2009), a routine maintenance of Sweden’s top-level domain .se went seriously wrong, introducing an error that made DNS lookups for all .se domain names start failing. The entire Swedish Internet effectively stopped working at this point. Swedish (.se) websites could not be reached, email to Swedish domain names stopped working, and for many these problems persist still.
According to sources we have inside the Swedish web hosting industry, the .se zone, the central record for the .se top-level domain, broke at
21:19 21:45 local time and was not returned to normal until 22:43 local time.
However, since DNS lookups are cached externally by Internet service providers (ISPs) and web hosting companies, the problems remained even after that. It wasn’t until around 23:30 local time last night that the major Swedish ISPs had flushed their own DNS caches, meaning that they cleared away the broken results so that new DNS lookups could start working properly again. If they had not done this the problem would have remained for a full 24 hours.
There are still a large number of smaller ISPs that have not yet fixed the problem. It is also likely that ISPs outside of Sweden is not aware of the incident, so the effects of the problem may remain there as well.