Nasa and the U.S. military are among high-profile victims of a new group of hackers, calling themselves 'The Unknowns.'

The group, who professes to use its hacking abilities as a force of good, contacted a range of security-conscious firms and revealed a list of passwords and sensitive documents that they had plundered.

t is unclear whether the companies affected even knew that their security systems had been bypassed.

The Unknowns posted the names and passwords of employees at Nasa's Glenn Research Center, the U.S. Military's Joint Pathology Center, the European Space Agency, Thai Royal Navy, the ministries of defense of France and Bahrain, Harvard University and the Renault automotive firm.

Bizarrely, FoxNews also reports that the group targeted the Jordanian Yellow Pages.

The hackers also posted screenshots of some of the sites they breached, in raids that date back to March.

The concept of hacking into companies to 'improve' their security systems is becoming more popular with hackers who want to justify their actions.

A similar stance has been taken by Malicious Security, or MalSec, a spin-off from whistle-blowing WikiLeaks.

In their e-mails to the companies affected, The Unknowns say their intentions were good - and say that they could have caused far more problems if they wanted to.

Addressed to 'Victims', the e-mail - misspelt and lacking punctuation - read: 'We have released some of your documents and data, we probably harmed you a bit but that's not really our goal because if it was then all of your websites would be completely defaced but we know that within a week or two, the vulnerabilities we found will be patched and that’s what we're looking for.'

It concluded with the promise that The Unknowns were 'ready to give you full info on how we penetrated threw your databases' if the companies contacted them.