Bull has a gadget for businesses worried about the security of data stored on laptops, namely a bootable, portable password-protected hard disk drive with an embedded cryptographic processor that protects data if the device is lost or stolen.

Globull (pronounced globule) is a bright red package about the size and weight of an iPod Classic. It has a colour display, houses a 60GB hard disk drive and has a USB 2.0 cable that wraps around the device for storage.

Plug it into any PC that can boot from an external USB 2.0 drive, switch on the computer, enter your password on Globull's tiny touch-sensitive pad beneath its display, and you have access to your regular working environment, applications and data. Switch off the computer again and you can take your data away without leaving a trace, according to Bull's marketing director, Bruno Pinna.

Globull's design means that users don't need to trust the PCs they use: They enter passwords directly on Globull, and the encryption keys never leave the device. The working environment is loaded entirely from the device, so there is no risk of observation or interception by malicious software on the PC, said Pinna.

Most recent PCs have the ability to boot from an external USB (Universal Serial Bus) drive - although IT managers may have chosen to disable this option in the BIOS settings for security reasons: It's not always desirable if staff can boot up an operating system of their choice, bypassing anti-virus or other security software installed on company PCs.

The 120-gram Globull package contains the hard disk and a cryptographic processor that scrambles data on the fly at 100MB/s, using the Advanced Encryption Standard with a 256-bit key (AES-256), protecting the data if the disk is lost or stolen. Without the password, the data cannot be decrypted.

Bull envisages a number of scenarios in which the drive could be useful to secure data: mobile workers with their own laptop; staff working on shared PCs, or for performing demonstrations on a client's computer. The company suggests installing a complete operating system - Windows or Linux - and applications on the device, but warns buyers to ensure that their existing software licences allow such a use.

Booting Windows from an external drive can be tricky, because it needs to know about peripherals and other hardware at the time it is installed, said Pinna. To get around that limitation, Bull offers an optional virtualisation layer for Globull based on Mandriva Linux. The virtualisation layer allows a Windows installation to run regardless of the hardware used.

For now, Bull is offering the device only in France, but despite the defence-level encryption it contains, there's no legal reason why it can't be sold elsewhere, said company spokeswoman Anne Marie Jourdain: Bull just preferred to concentrate on France first, and an international launch is planned for the second half of the year, she said.

Globull has a price tag of 460 euros ($685) for the basic version, but the price is negotiable in quantity, Jourdain said.

The virtualisation layer adds 80 euros to the cost, Pinna said.

By year-end, Bull hopes to offer a higher-capacity model with a 120GB disk. Other authentication methods are also being considered, including a version with a fingerprint reader.