Twitter had a service outage Friday morning because its DNS servers were compromised. It was done by a hacker or group of hackers self-identified as the “Iranian Cyber Army.” The group also took over the Iranian opposition Web site mowjcamp.org. Twitter is investigating the issue, said company cofounder Biz Stone. At press time, Twitter was back up and running, but the mowjcamp.org site was not. Twitter’s records were compromised last night, but they had been fixed by the time Stone posted comments at 11:43 p.m. Pacific time on his blog.