Everyday Security in an Online World

Back Up Your Data

Backup means keeping copies of your files in case the originals are lost or damaged, for example by software problems, malware, disk failure, fire, theft, or human error.

While not strictly a security topic, backup goes hand in hand with security because we must acknowledge that however hard we try to protect our devices and accounts, they may one day be breached — and our documents, photos and other data destroyed maliciously. Having a recent backup of one’s data stored elsewhere means it can be recovered once the device or account has been made clean.

By keeping backups we can be more confident using our computers, and less fearful of making mistakes, knowing that we have this insurance policy in place.

Frequent and automatic

Consider that the files you least want to lose will often be current projects or those you have worked on most recently. This means that to be useful, backups should happen frequently so that the backed up files are an up-to-date reflection of your work in progress.

As an example, the built-in backup software on Mac computers, called Time Machine, runs hourly. This might sound like an onerous task for the computer if you have a lot of data, but in fact, like most backup processes, Time Machine performs incremental backups — meaning that each time it runs, it only backs up new files or files that have changed since the previous backup.

Consider also that making backups isn’t the most exciting thing, and that humans have a tendency to procrastinate routine maintenance tasks — like testing smoke alarms, or pumping up the tyres on a bicycle that are starting to go a bit flat. For these reasons, it helps to have backups take place automatically.

Local backup

With local backup the copies of your files are stored on an external hard drive or flash drive (memory stick) which you physically connect to your computer. Be sure to choose a drive that has considerably greater capacity than the total size of your data, to allow multiple historic versions of files to be kept — as well as for future growth.

It’s important to note that the drive simply acts as a container for backed up files, and doesn’t actually do any backing up by itself. You need backup software on the computer, and you need to instruct it to use your chosen drive as the store for the copied files.

If you have a Mac, I recommend using the built-in Time Machine backup software because I have found it to perform consistently well since its debut more than a decade ago. It’s also extremely easy to set up and use. If you have a Windows PC your options are numerous, but because of my mixed experiences with different products and because of how they change over time, it would be unwise of me to make any particular recommendation here.

Local backup doesn’t apply to tablets or smartphones.

Online backup

With online backup the copies of your files are stored by an IT company of your choice. They might call it the cloud; in reality, this means warehouses called data centres filled with servers with very high-capacity disks that store backups for thousands or even millions of people. The data centres are often distributed around the globe and configured such that your files remain available even in the event of a power failure, natural disaster, or other major incident affecting one location.

Windows includes OneDrive, which is Microsoft’s cloud storage platform and can be used for online backup of your documents and pictures. Apple’s equivalent is iCloud Drive, which is built into macOS. Numerous similar options exist; well-known examples are Dropbox and Google Drive.

As well as being simple to set up, what these services have in common is that their primary purpose is to sync your files between multiple computers, if you have them, as well as with tablets and smartphones. Backup and sync go hand in hand because in order to make your files available across all your devices, the service stores its own copy of your files in the cloud. In the unlucky event that all of your devices are destroyed simultaneously, for example by fire, you can sync your files from the cloud onto a replacement device. In a pinch, you can also access your files in the cloud from a friend’s computer.

Many online backup services are free up to the point where you wish to store more than a certain amount of data. If your files are primarily documents and spreadsheets, you may never reach this point. But if you have lots of photographs, you might need a paid subscription from the outset in order to keep them all backed up.


A limitation of relying on simpler file syncing services for online backup is that most of them aren’t designed to keep old versions of edited or deleted files, especially in the longer term. This may limit your means of recovering from human error: if you mistakenly delete a file on one device, for example, the service will dutifully delete it from your other devices too.

More comprehensive backup services offer versioned backup, meaning that when you make edits to a document or crop a photo, for example, they don’t replace the backed up copy with the edited or cropped one. Instead, they keep both. Similarly, when you delete a file, the service notes that it should no longer be included in the current snapshot of your data, but retains it as a historical record. This gives you something akin to a long-term ‘undo’ facility — in the event you decide you preferred a file how it used to be, you can ‘go back in time’ to recover it. If this sounds important to you, and especially if you’re not also making local backups, you should research the versioning capabilities when choosing an online backup provider.

Belt and braces

I advise people to combine both local and online backup because they mitigate different risks. For example, if fire destroys your local backup along with your computer, you can restore from your online backup. If someone breaks into your online backup, the local backup is unaffected.

Air-gapped backups

Historically it has been common practice to leave one’s local backup drive connected to the computer all the time. This way, backups can take place fully automatically. But the rise in ransomware, since around 2012, presents a challenge to this norm.

Ransomware is a kind of malware (see Only Open Trusted Apps and Files) that encrypts the documents, pictures and other files on your computer – meaning they are scrambled and useless without a ‘key’ – then demands a large sum of money for that key to decrypt them. Backups provided an easy way to avoid paying the ransom, so it wasn’t long before ransomware creators adapted their malware to seek out and destroy local backups as well.

Even if you can afford the ransom, there are three further pitfalls. First, the criminal might just take your money and not give you the key. Second, the ransomware might be badly made and unable to decrypt your files even with the key. Finally, by paying the ransom, you are sustaining the criminal’s business model, encouraging them to go on perpetrating ransomware attacks — and possibly funding other kinds of organised crime.

Companies that make operating systems and backup software are fighting back, creating innovative ways to protect local backups from ransomware. But it’s the nature of the game that criminals will sometimes be one step ahead. Furthermore, as you now know very well, software is never perfect and people make mistakes.

The only way to be completely certain that a local backup cannot be destroyed by malware is to physically disconnect it from the computer. This is referred to as an air gap: you can visibly observe the nothingness between your computer and the unplugged backup drive on the other side of your desk! Better still, put the drive in another room, so that if a burglar finds your computer they don’t grab the backup disk too; or if your house catches fire, there is a greater chance of either your computer or your backup disk remaining intact.

Naturally, once your backup drive is disconnected you can no longer make backups! So a compromise is required. Set a reminder in your calendar to connect your backup drive, say, once a week to bring it up to date. When you’re also using continuous online backup, reducing the frequency of local backups to weekly or less is quite acceptable.

Testing it

In your workplace, or when staying in a hotel, or perhaps back when you were in school you have most likely taken part in a fire drill. This not only checks that the alarms are working, but gives people practice in efficiently evacuating the building, so that if one day a real fire occurs they are sufficiently rehearsed in what to do.

In a similar but less dramatic vein, you ought now and again to pretend you’ve lost a file and need to recover it from your backup. In doing so, you’ll check both that the backup is working and contains a copy of the file, and that you know how to retrieve it. Pick a recent file for your test, to confirm that the backup is up to date.

You should also learn how to check the status of your backup as reported by your backup software or cloud service. It should tell you something like “OneDrive is up to date” or “Latest backup: today at 15:05”. In an ideal world, this is the only check you’d need to make; in practice, it’s still worth doing the fire drill once in a while.

What you can do

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