BitDefender Internet Security 2009's low cost is a major plus point – at £29 for a year-long licence for three users it is one of the least expensive internet security suites. Its strong showing in heuristic tests does it no harm either.

Such tests simulate how well a suite can detect new and unknown malware. But while BitDefender fixed some annoyances that marred the previous version of the suite, BitDefender Internet Security 2009 has some rough edges.

BitDefender performed very well at catching malware, snagging 98.9 percent of AV-Test’s collection of Trojan horses, bots and other malware. This is a small but welcome improvement on its previous score of caught 97.2 percent for this test, but still ranked it only fourth.

However, BitDefender Internet Security 2009 did better than most rivals in proactive tests that use two-week-old signature files. It spotted 52 percent of malware, a result bettered only by the G Data suite.

Only one false-positive warning was thrown up, while BitDefender Internet Security 2009’s ability to scent rootkits was superb. In fact, it managed to detect and remove all the inactive and active samples of stealth software that put it up against.

BitDefender also did well at cleaning up existing malware infections, successfully eliminating all of the files for every infection but one. However, for half the infections it left in place some Registry changes (which are far less likely to hurt anything when left behind), and its scan speed was in the middle of the pack.

We were pleased to find some helpful changes to BitDefender Internet Security 2009's interface. For one thing, straight after installation we were warned that our test laptop was using an unencrypted wireless network. The suite can also recognise when you attach removable storage such as a USB flash drive and will ask whether you want to scan the device. If the pop-up annoys you, you can tick a box to prevent BitDefender from showing it again, but we liked having the option.

Counterbalancing those good points, however, are some annoyances. Although BitDefender Internet Security 2009’s firewall refrains from bugging you about allowing some known applications to connect to the internet, we received a warning about the lesser-known FileZilla FTP program.

Also, we encountered an apparent bug in which the Windows Security Center declared that the suite was out-of-date, despite its having received an update 40 minutes prior; a reboot cleared the false alarm.

BitDefender includes a useful vulnerability scanner that can identify missing Windows or application patches, but the company appears not to update its version list as quickly as it should. The tool reported the correct installed Firefox version (3.0.4), but said that the latest version available was 3.0.1. We probably wouldn’t have been notified if we had had an out-of-date browser.

An expansive parental-control feature provides options for restricting access to websites and installed programs, and it can also watch for certain keywords in web pages and email messages or deny IM chats with particular contacts.

In our usage tests where we attempted to download Zango adware, the parental-control feature prevented the browser from downloading the file, but it didn’t provide an alert or any other notification that it was blocking the attempt.

This kind of quirk could cause some confusion. When we turned the parental controls off, the suite’s regular file protection blocked the download from saving to the hard drive - and it displayed the expected pop-up, too.