A hacker claiming to be a member of the loose hacking collective Anonymous took credit for knocking offline the website of the cloud storage provider Dropbox late Friday. Attempts to reach the site were met with an error message.

But the company said that the site went down because of a problem that arose during regular maintenance, not because it was compromised by hackers. The site was back up before midnight on Friday.

“Today’s outage was caused during internal maintenance, and was not caused by external factor,” a company spokeswoman said in an email. “We apologize for any inconvenience.”

Still, hackers tried to claim credit, saying the error was the result of a security vulnerability in the website.

Hackers who call themselves AnonOpsKorea, a Korean offshoot of Anonymous, said one of their affiliates, using the Twitter handle 1775Sec, was responsible. In a post on Twitter, that individual said the attack was intended to avenge the death of Aaron Swartz, the renowned programmer and charismatic technology activist who committed suicide last year while facing a federal trial on charges of hacking into the M.I.T. computer network.

The hacker claimed to have compromised Dropbox’s site using a security vulnerability and threatened to dump Dropbox data if the company did not plug the hole that allowed for the site compromise. “We are giving you time to fix your websites vulnerability. If it’s not fixed expect a Database leak!,” 1775Sec tweeted.

Later, the hacker offered a link to what it said was a partial leak of information. But Dropbox said the information was posted a month ago and wasn’t the company’s information.

The Dropbox spokeswoman said there was no loss of customer information.

“In regards to claims of ‘leaked user information’ – this is a hoax,” she said. “This is not Dropbox data.”

New York Times