Nonetheless, the similarities are startling. In return for an annual sum, an organisation agrees to protect you against unnamed threats from unknown sources. You pay on trust – and if trouble comes knocking, the protection agency steps in to sort it out. But you don’t really know if the threat was real or imagined.

The problem with this arrangement is that you can get the same level of protection without paying a penny, and that’s why the biggest antivirus vendors are in the habit of automatically renewing your premium before you have the chance to go shopping around.

But that may be about to change. The UK’s competition regulator, the Competition and Markets Authority, has taken what it says is the unprecedented step of starting court proceedings against one of the biggest vendors, over claims it refused to cooperate with an investigation.

Norton, whose antivirus software comes preinstalled on many computers, and is offered as a package by some high street chains, is being investigated over concerns that its terms and practices for automatically renewing contracts could lead to customers paying for services they no longer want or need.

The Authority has been investigating the sector since November 2018, and says Norton’s failure to provide it with details on how its customers respond to auto-renewal and pricing amounts to a breach of legal obligations. It is the first time in a consumer protection case that it has had to resort to the courts.

Norton says it is confident its terms are “fair and compliant with UK consumer law”. But however the matter is resolved, the fact remains that there are cheaper – and no less effective – alternatives to anything from the big commercial vendors. And though the importance of having antivirus software on a PC cannot be overstated, there is no reason to pay a penny for getting it.

Assuming your computer is for personal use, including working from home, you can download and install free versions of programs by AVG, Avast, Kaspersky and a few others. But you may have to comb through several web pages before you find the right product, because the vendors would rather sell you their premium, paid-for alternatives. Kaspersky’s site goes out of its way to hide its free Security Cloud product – and when you do find it, it appears to be unrecommended; in fact, it’s one of the best out there. The add-ons that come with the paid-for versions are mostly just fluff, but AVG and Avast throw in a few for free.

You may also find that your broadband contract comes with free antivirus protection by McAfee or one of its rivals, for as long as you stay in contract. Plusnet is one of the providers to offer this.

Installing a free programme is simply a matter of downloading it. But pay particular attention to the various set-up boxes and avoid anything which is labelled a free trial; it may be there to trick you into signing up for a premium version which will stop working after a few weeks, unless you start paying. Stick with the all-free variants.

The only downside with the free products is that they tend to be more visible than their paid counterparts. But it takes only a few tweaks in the settings screen to get rid of any nag screens you find intrusive.

What you won’t find with free protection is a helpline. But if you do run into a virus, you’ll find instructions to get rid of it on the AVG, Avast or Kaspersky websites. And, for the record, the first thing they will tell you is never to pay anyone any money for protection.