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External storage media such as USB sticks, portable hard drives or CDs/DVDs are in everyday use with computers today. What happens though if such storage media containing your sensitive data are lost or infected with a virus?


Always use external storage media securely, by …  
Info sheet: Safe use of external storage media
  • encrypting sensitive data
  • securely deleting sensitive data
  • deactivating the autorun function

Risks inherent in using external storage media

The advantage of external storage media is that they are mobile - they fit into any bag or pocket and can easily be taken with you anywhere. However, there is also a higher risk of loss or theft, so that it is vital that you encrypt your sensitive data on external storage media, and always keep a copy of all such data at home. You can read up on how to easily encrypt your storage media at the end of this report.

External storage media are particularly handy for data back-ups. However, please remember that these media don’t last forever. There are hardly any historical data on this so far, but it is estimated that USB sticks will probably last up to 10 years, hard drives up to 10 years, and CDs/DVDs most likely between 10 and 20 years. Their service life however is only one issue to be considered – you must also ensure that you will still be able to read your data in the future, and that the systems and readers required to do so are still in place.

In case you no longer need some of your external storage media and would like to dispose of them, please be aware that this could lead to your sensitive data ending up in the wrong hands. Make sure that you securely wipe your storage medium before you dispose of it.

A risk of a totally different, yet no less threatening nature is malware (viruses, worms, Trojans etc.), which might be present on your external storage medium and can automatically install to your system when you connect such a storage medium to your computer.

If you are running Windows with standard settings, a selection menu showing different options on how to handle the data on the storage medium appears when you connect it. So far, so good - but there's other things happening in the background, too: Windows is also searching the drive for a file called «autorun.inf», which - if present - it will execute without any further actions by you. This can be the perfect gateway for malware to enter.

The situation is a bit different with macOS: No autorun function is implemented when connecting a device to your USB port - yet this can still happen with CDs/DVDs, and this feature should be deactivated. You can find out how to deactivate the autorun function in both Windows and macOS towards the end of this report.

To generally protect yourself against viruses, you should safeguard  your system with current antivirus software, which must be kept always up-to-date.

Encrypt sensitive data!

Every time you transport data on external storage media, it is vital to protect them against unauthorised access. In addition to such optional processes as file passwords, many USB stick and portable drive manufacturers provide their own software just for this purpose. In addition, there are some alternatives available on the Internet.

Deactivate autorun function!

It is quite easy to temporarily deactivate the autorun function under Windows. Just press the shift key on your keyboard and hold it down. Then connect your external storage medium to your computer, releasing the shift key a short time later. In this case, the shift key prevents Windows from immediately executing programs and files on your external storage medium.

It is quite complex to permanently deactivate the autorun function in Windows, but this should neverless be done. With regard to the settings required to do so, this depends on the version of the operating system you’re using, and which updates you have installed. You will find instructions on how to do so under Microsoft. Please note that these settings will completely deactivate the autorun function, i.e. for USB sticks, portable hard drives and CDs/DVDs as well.

With macOS, it is very easy to permanently deactivate the autorun function for CDs/DVDs. You can adjust these settings under Control Panel - CDs & DVDs. As already mentioned, you cannot change any settings for USB sticks and portable hard drives though.


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