Norton Internet Security (NIS) is one of the best-known names in anti-virus and security software.

However, we’ve often heard complaints from users who have been annoyed by the fact that it was prone to slowing down the computer when running its scans, and by the messages that pop up offering warnings or advice.

So for the new 2009 edition, Norton's maker Symantec has primarily concentrated on performance, rather than simply adding new features. We wouldn’t go so far as to say that NIS 2009 is ‘zero impact’, as Symantec claims, but we did find it a lot less intrusive than previous versions of the program.

The improvements start from the installation, which took us just one minute to perform on our test notebook (it actually took us longer to complete the online registration). When it’s running, NIS 2009 only uses 7MB of memory, so it doesn’t take up a lot of resources that might be needed by other programs.

And if you’re playing games or watching video and don’t want to be interrupted for a while you can right-click on the Norton icon in the Taskbar and activate the new silent mode. This temporarily stops messages from appearing on screen and tells the program not to download any new updates.

In addition to the regular four-hourly checks for information about new viruses, there are new so-called ‘pulse’ updates that can perform a quick check every few minutes just to make sure there have been no recent updates that need to be installed.

If you’re worried that your PC might have been infected, NIS 2009 includes a new module that performs a very quick scan just to check that everything is OK, which on our PC took only 43 seconds.

The quick-scan option uses a new feature called Insight that checks the files on the computer against an online database of known and trusted files. Files that are a normal part of Windows are included on this list, so NIS skips past these to save time and only check files that it doesn’t recognise.

There's still the option of running a full scan for maximum security, and such scans can also be set to automatically run when you’re not using the computer.

So while Norton Internet Security 2009 doesn’t provide many new features, its focus on improving performance and minimising distractions is very welcome.

Our main complaint is that there’s no printed manual, and we sometimes struggled to find our way through the online Help files to locate specific features. However, with 24-hour online chat and telephone support now available, there is the comfort of knowing that there’s someone ready to help when you need it.