Twitter is down for an hour Thursday morning shutting millions of users from using the online messaging service.

A message from twitter's blog read:

Twitter is the target of a denial of service attack. Attacks such as this are malicious efforts orchestrated to disrupt and make unavailable services such as online banks, credit card payment gateways, and in this case, Twitter for intended customers or users.

This is the first major outage of Twitter service; all users around the world were affected.