If you use free cloud services to store or share your files to others, you have to expect a catch. Usually it means your data is collected for advertising purposes.

Even if all you have to do to use a service is to enter an email address, that doesn't mean that your data isn't being collected, the experts say. More likely the email addresses of senders and recipients will end up in some database.

It's also possible that the files you exchange are analysed and perhaps not even deleted after a transfer but instead used in conjunction with the email addresses to build user profiles.

In return for a free service you can expect that the provider shows adverts, tracks users or uses plug-ins from Facebook or Google.

If you place any value on your personal privacy, especially when it comes to sensitive photos or documents, you certainly shouldn't rely on the encryption offered by a free service but rather should encrypt your files yourself before uploading them to the cloud.

Free cloud services may promise automatic encryption and decryption but it's often unclear what technology is used and whether security is really guaranteed.

 - dpa