SanDisk has unveiled a USB Flash drive that automatically backs up every file copied to the drive to an online server.

The company claims that its Cruzer Titanium Plus provides users with the " best of both worlds" as data is always available.

Users can access files as usual by plugging the drive into a computer, or access backed-up files through any computer connected to the internet if they forget the drive or it is lost or stolen.

The Cruzer comes with six months' free online backup, after which it costs $29.99 a year.

After opening a personal password-protected online account, any files copied to the drive are automatically backed up online.

If the computer is not online when files are copied to the drive, the backup will take place the next time there is an internet connection.

Files deleted from the drive will be kept online for 30 days, as long as the total of backed up files from the device and deleted files do not exceed the physical capacity of the drive.

"This is true 'set it and forget it' data protection," said Hezy Rotman, vice president and general manager of the USB Division at SanDisk.

"Many users have told us they worry about losing their data, and now SanDisk is reducing that anxiety through an innovative new form of online backup."

The drive can be password protected for added security, preventing other people from accessing data if the drive is lost or stolen.

The Cruzer Titanium Plus will be featured at the upcoming CES show in Las Vegas and is expected to be available in the US in March for $59.99.