Buying a second-hand PC, what are the risks and how can you make sure it’s safe?

If you’re in the market for a PC and you’re considering a second-hand machine there are a number of things you should take into consideration before you make your PC purchase.

There are several cases for considering a pre-owned laptop or PC. Whether you’re a first-time buyer who doesn’t need the latest and fastest machine or a super-user who knows exactly what you’re looking for and you’ve found someone who is selling up their pimped-out PC with all the extra bells and whistles – you need to know what the dangers are and how to protect yourself against them.

What to look out for when buying a pre-owned PC

Firewall / anti-virus updates

How did the previous owner take care of his/her machine? Did they meticulously maintain their firewalls and ant-virus software or could there be nasty malware lying dormant inside it?

Who is the previous owner?

It has been known to happen that less than savory individuals will intentionally load malicious software or spyware onto the machine before selling it with the express purpose of accessing, harvesting and abusing your delicate data. From banking details to personal information, pretty much anything you input in your machine (or anything which has been saved to your accounts and profiles which you then access from the machine) could be harvested with the correct malware installed.
Other times the previous owner may be oblivious to the fact that they are selling you an infected machine as they themselves were being hacked.

Deleted Files

If the previous owner had illegal downloads or torrents which have been deleted, they could easily still be hiding inside your machine. A good IT technician would be able to find these deleted files without too much trouble at all. You wouldn’t want to end up being incriminated for something which you didn’t know was sitting on your machine before you ever laid a hand on it.

Types of malware that could be on your pre-owned machine


A key-logger tracks everything that’s inputted to your keyboard and relays it back to whoever is behind the malware. This includes your usernames and passwords. The thing that makes key-loggers especially risky is the fact that they are almost impossible to detect while you’re using your machine.


Another common form of data theft is through the installation of spyware. This could take regular screenshots, or access your webcam. However, this kind of malware is somewhat more advanced than a key-logger and it’s unlikely that a previous owner would install it on your machine unless they knew for certain that the new owner were going to use it for accessing lucrative information – for example, if they know it will be for business use.


As the name suggests, cryptominers are software that mine cryptocurrency. Mining cryptocurrency uses a fair amount of processing power, so what happens is malicious miners will install the software secretly and basically hijack your PCs processor to work for them while you’re using your machine. The chances are the only thing you would notice is that your machine is running a little slowly while its resources are being redirected to crypto-mining.
Aside from the obvious speed issues, the problem here is that even if your own data is not abused, you could end up in trouble for running (often illegal) software which you don’t even know was on your machine.

Pro-Tip: New machines can be pre-loaded with malware just as easily as a second-hand one. Even if you are buying a new laptop or PC, you should follow the steps outlined below to ensure a safer user environment.

How to clean your Second-hand Computer before you use it

Erase the Hard Drive

The first thing you want to do is wipe the hard drive. If there is anything lurking in your newly-acquired machine this is where it’s likely to be found.
That said, a drive is a difficult thing to erase (just ask any criminal who was ever caught using the info contained on what they hoped was a wiped drive).
Luckily there are several “cleansing” methods you can make use of. They might not erase all digital footprints from the machine, but they should at least take care of malware.
Try DBAN. This free data destruction program should be burnt onto a disc before you run it. Then you simply run the disc and it will kill anything that’s in there.

Reinstall your operating system

Another way to make sure your machine is running as the factory intended is to uninstall and then reinstall your operating system (probably Windows).
This does depend on your machine coming with a Windows install CD(if it has an older version of Windows). Or download Windows 10.

Use your own anti-virus

It’s a good idea to choose and install your own firewall and anti-virus software rather than trusting to whatever is installed on the PC when you get it. There are several free options, or you can choose an inexpensive paid firewall like this one and be assured an easy user experience and superior security.

Surface clean

This may sound like a “No Brainer”, but along with your software being “hygienic”, you want to take care of your actual hygiene, too! Keyboards can be dirty, dirty things. With the machine turned off, use a computer cleaning spray and give the entire machine a good wipe down before you use it. You can even take a soft toothbrush to clean between the keys.

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