Given the regularity with which laptops, USB Flash Drives and other portable media are lost, left lying about or simply stolen, it makes sense to protect the data they're carrying, even if you can't look after the physical devices themselves.

Like everything people don't want to do - backing up or taking out insurance - the key to protecting data is to make the process simple and transparent, so you don't really have to do anything and it doesn't make all your machines run like treacle.

DeviceDefender goes some of the way towards achieving this by allowing you to set up 256-bit AES encryption on any removable drives including USB sticks, hard disks, CompactFlash, SD, MicroSD and Memory Sticks; encryption to this level is tough enough to have been adopted by the US government.

Once you've installed the software on your PC, the first time you plug in a removable disk Device Defender wakes up and goes to work. Having created a password (and a hint question and answer in case you forget it) the program then displays three options: always encrypt any unprotected files that are found, encrypt any unprotected files just this one time and only encrypt new files as they are written.

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This flexibility makes it easy to protect information already stored on a disk that needs to go out of the office either just the once or more frequently, or to encrypt an empty device that's going to be used to bring sensitive files from the outside back into the office. At the same time, it copies a small program - called Open Secure Files - to the disk that allows PCs without DeviceDefender to access the encrypted information.

Plug the newly encrypted disk into another PC and it appears in Explorer with a locked icon. From here the files can only be read by double clicking the Open Secure Files program icon and entering the password. Although existing files created on the original PC with DeviceDefender installed will be re-encrypted automatically if you work on them and then write them back to the disk, any new files created on a PC without DeviceDefender won't be.

However, the Open Secure Files program includes an Explorer-style program which makes it easy to copy files on and off the disk and includes the option to encrypt new files manually, on the fly. This is straightforward, a bit like adding a file to a WinZip archive.

The consumer version reviewed here lets you create as many secure disks as you like, so the data for a whole family or a small office can be stored and transported securely by installing DeviceDefender on one PC and creating the disks from there.

Drawbacks? It doesn't play nicely with iPods set up as disk drives (the usual setting for the diminutive Shuffle) and produces access privilege error messages, sometimes copying music and podcasts and sometimes not. This won't be a problem for corporate users where you're not usually allowed to plug in personal devices, but smaller, more relaxed businesses and home users will find it irritating.

And encrypting/decrypting data introduces another layer into the open/save process which inevitably slows things down; opening and closing Word files a few pages long isn't a problem, but saving a new 800MB file to an encrypted disk took us about 35 minutes.

Still, at less than £30, DeviceDefender offers users who need to transport sensitive data around on removable devices a decent solution that's robust, easy to implement and has industrial strength protection.

There's a performance hit when encrypting and decrypting files and it's not fond of iPods set up as disk drives, but for the money, this is a strong, secure means of protecting data stored on removable devices.