However, there are plenty of free antivirus software solutions on the market, many of which are just as capable as their commercial cousins. So if you're tired of annual subscriptions, read on - I've picked out nine of the best free internet security tools to deliver great security at no cost.
The program is simple to install; a straightforward interface makes it easy to use; a quick first scan should identify any potential threats on your PC, and this all has minimal impact on your system performance.
Avast recently added a "Grime Fighter," which the company says supports 12 additional languages and offers an advanced console for more user control.
It's the free version of a commercial product, and so has a few missing features. The Pro edition helps to protect you at public wifi networks, for instance, while its "USB Vaccine" function reduces the risk of malware infecting a USB drive.
The core antivirus protection remains the same, though. And while that doesn't deliver the top detection rates, independent testing shows it's very capable, with the program winning certification in AV-Test's latest report.
A strong antivirus engine (rated highly by independent labs for its file detection rates) constantly monitors your PC, looking for and eliminating threats.
If you choose to install the Avira toolbar then you also get some web tools (an antiphishing tool, ad blocker, social networking protection), although this also replaces your default search engine with an Avira page.
Problems? The interface can seem a little complex, just at first. And the program has more impact on your PC's performance than some other tools. Still, on balance Avira Free Antivirus remains a capable and effective security package.
Avira recently made available the Avira Protection Cloud (APC), which will be used to detect and thwart zero-day attacks, according to the company. The technology will be available to all users of the free software by the end of May.
The program does provide plenty of functionality, though, with a capable, AV-Test-certified antivirus engine, an easy-to-use firewall and some browsing protection.
It does its best to keep things simple. Open the Preferences dialog, say, and you'll find only 10 buttons and settings (and most of those you'll never need to use).
The database update means it wouldn't be our first choice, but if you're a fan of ZoneAlarm, or just want a firewall and antivirus tool from the same company, this could be a good choice.
The program is ultra-compact, downloading and installing in less than a minute on our test PC (although it does demand removal of any incompatible products first). A very basic interface then provides effective on-demand and automatic scanning, real-time antivirus and antiphishing protection.
At first glance this makes the program seem more complex, as there are lots of tiles, buttons and menu entries. Smart interface design means you can carry out most common actions in a click or two, though, so you'll soon feel at home.
AVG Free Antivirus gets mixed reviews on its effectiveness: AV-Comparatives rate it as average, AV-Test say it's better than some commercial suites. My view: it's a capable, feature-packed tool, and one of the stronger free antivirus packages.
To boost its offering, AVG recently released the AVG Zen tool, which the company claims is designed to help provide added protection across desktops and mobile devices.
The program runs without requiring installation, reducing the chance of any conflicts with your existing antivirus package.
Its straightforward system scanner uses a dual-scan-engine, rated highly by Virus Bulletin (and which did actually achieve a 100% detection rate in a recent AV-Comparatives test).
The program can be installed in two modes. The standard option provides a good range of tools: an antivirus engine, simple parental controls, an application firewall, vulnerability scanning and more. But you can also run FortiClient without its real-time protection, perfect if you need to run it alongside an existing antivirus tool without conflicts.
My tests suggest it's not the best antivirus engine around, but is still worth having. AV-Test and AV-Comparatives confirm that it's a good mid-range contender, and FortiClient could be particularly helpful if you want a second-line tool to run alongside an existing antivirus engine.