If you find your computer has a virus, or other malware, the first thing you'll want to do is get rid of it. 

Obviously, your antivirus package is a good starting point, but given that it missed the problem in the first place, you might want a second opinion. 

There are steps you can take to improve your existing security software, such as updating it to include the latest malware fingerprints, but there are free tools online to help your peace of mind, acting as a safety net in case your original anti-virus protection lets you down.

Want to make sure your computer is protected? Read our Which? reviews of the best antivirus software.

Using your own anti-virus software

Security packages on your computer offer good protection, but they need updating regularly to make sure they know the latest malware and viruses doing the round. 

If you think you have a virus infection, even before running a scam, the smartest thing to do is to update your antivirus database. Most security software suites have an 'Update' button or similar, and clicking this will prompt the software to update against the latest threats and viruses.

Once the update has run, perform a full system scan. If you're running a laptop, ensure that it's plugged into the mains so it doesn't run out of power part-way through the scan. If there are any threats lurking on your system, this process ought to spot them.

Second opinion: Malwarebytes

If your antivirus doesn't pick up the problem, Malwarebytes Free Anti-Malware offers another set of eyes. You can download and install the program for free from Malwarebytes' own website. 

Read our full guide on how to scan with Malwarebytes

Installing antivirus software with no internet connection

If your computer has a nasty bug, it might not allow access to the web, so downloading anti-virus updates or Malwarebytes may not be so simple. 

In this case, you could try using a separate PC, a friend's or neighbour's if there's not another computer in the house, to download the software to a USB key to attempt a recovery. 

It may be necessary to start up your computer in Safe Mode to install and run the antivirus software. Malwarebytes includes instructions for this, but it requires a level of technical expertise.