Despite the security risks, more employees in the future are expected to use services, mobile devices and other new technologies outside the control of IT departments. Gartner predicts that in less than three years, 35% of enterprise IT expenditures will occur . As a result, many experts advise companies to abandon their command-and-control strategy and adopt a more cooperative tactic to deal with workers looking for the easiest way to get their jobs done.

Dropbox's changes should improve security to users' accounts, and other companies such as Google, Facebook and Microsoft, have already implemented many of the same features, Wisniewski said. As an added precaution, users of cloud-based storage should rely on tools, available from security vendors, for encrypting data before it is stored in the cloud.

"Personally, I don't store anything in the cloud that I wouldn't want publicly accessible unless it is encrypted," Wisniewski said.

Dropbox is one of many free or low-cost file-sharing services available to consumers and businesses. Competitors include ADrive, Box.net, Flickr, Carbonite, Google Gmail, Mozy, SugarSync and YouSendIt.

in CSOonline's Cloud Security section.