IBM has banned employees from using Dropbox and Apple's iCloud at work as it claws back permission to use third-party cloud services. The rethink has also resulted in a edict against the iPhone 4S's Siri voice recognition technology at Big Blue.

Jeanette Horan, IBM’s chief information officer, told MIT's Technology Review that the restrictions had been applied following a review of IBM's Bring Your Own Device (BYOD) Policy, introduced in 2010.

IBM still supplies BlackBerrys to about 40,000 of its 400,000 employees, but a further 80,000 others now access its intranet using rival smartphones and tablets, including kit they purchased themselves. The initiative has not yielded anticipated cost reductions even though it has created various security headaches.

An internal survey of IBM workers discovered they were "blissfully unaware" about the security risks from popular apps, according to Horan. In some cases, staff forwarded internal corporate emails to webmail inboxes, potentially pushing sensitive information beyond Big Blue's security perimeter.

Horan's team has set about establishing guidelines on which apps IBM workers can use, which among other things discourages the use of Dropbox while encouraging the use of IBM's own cloud storage service, MyMobileHub.

Employees' devices are specially configured (normally over-the-air) before they are allowed to access IBM's network. Changes are made so that a smartphone can be erased remotely if it is lost or stolen, for example.

IBM disabled Siri, Apple's voice-controlled search engine, on employees' iPhones because of concerns that spoken queries, which are converted to text and processed on Apple's servers, might allow sensitive information to leak into third-party systems.

"We're just extraordinarily conservative," Horan says. "It's the nature of our business."

A proportion of workers are allowed to access IBM email, calendars, and contacts on their portable devices, while others are given wider access to intranet applications and data. The smartphones and tablets of users in the latter category are loaded with VPN client software so that communications are encrypted.

Bill Bodin, IBM's chief technology officer for mobility, added that whatever the challenges of supporting workers' equipment might bring, reversing BYOD practices is not an option for IBM nor the business world in general. "The genie is out of the bottle," he said. ®