Berlin  - It's become ever easier to save a document with Google or a picture with Flickr thanks to the quick spread of online storage services, known as the cloud.

Quite simply, the cloud allows users to dispense with purchasing their own software or extra memory. Instead, they can access programmes and storage space offered by third parties online, even if those functions are stored on computers that are on a different continent.

The bonus is that the data is then accessible from anywhere in the world. Plus, users can skip buying expensive software. But there are risks of storing your files on someone else's computer, especially when it is far away.

"In general, cloud computing is not unsafe," says Stefan Katzenbeisser of the computer science department at the Technical University of Darmstadt in Germany. The more important question is how the service provider goes about storing data.

Customers with T-Mobile USA recently suffered data losses when files stored with the smartphone service Sidekick got lost during maintenance on a server. "But that's not a problem of cloud computing," says Katzenbeisser. It's a problem with the way the data is stored.

A secure backup means saving data two or three times at different locations, which should be common practice. Anyone who wants to save data online can check with a provider about their practices, notes Katzenbeisser. But if a third party is subcontracted to do server maintenance, the possibility of mistakes increases.

Katzenbeisser sees clear benefits to cloud computing for businesses. "It means I probably don't need to set up a new infrastructure and can save on resources."

But he's sceptical of the benefits for private users. "I still don't understand why I should save private photos on the internet." Nonetheless, using the cloud means computers can access the data from any internet-connected device, assuming the data hasn't been lost. (dpa)