NASA acknowledged an attack on one of its websites by "The Unknowns," a group that has been publicly trickling information on websites it has hacked over the last few weeks.

The Unknowns claimed to have hacked a NASA website hosted at the Glenn Research Center on May 1, said Sally Harrington, a public affairs specialist with the centre in Cleveland, Ohio.

"NASA security officials detected an intrusion into the site on April 20 and took it offline," she said. "The agency takes the issue of IT security very seriously and at no point was sensitive or controlled information compromised."

The Unknowns posted a wrap up of several weeks of hacking on Pastebin earlier this week, claiming to have also hit a subdomain belonging to the US Air Force, the French Ministry of Defence and the European Space Agency, among others.

The group also claimed to have hacked the Bahrain Ministry of Defence, but the website actually belongs to the Ministry of Development in Brunei, a small nation on Borneo next to Malaysia.

The Unknowns released about 215MB of documents that it said came from the US Air Force. The information varied from receipts for expense reports to documents related to emergency communications plans. Many documents were dated 2012, and some carried the label "unclassified." US Air Force officials did not have an immediate comment.

The Unknowns wrote on its Twitter feed yesterday that "we're soon going to email our victims informing them on how we penetrated their databases, they will get all the info they need."

On its Pastebin post, the group gave a bit more insight into its motives, saying to the websites affected "we probably harmed you a bit but that's not really our goal." They said if they wanted to do harm, the websites would have been defaced.