AVG Internet Security 8.5 is a free upgrade for existing users of the popular suite, and as the name implies it isn't a completely new version. What it does add, though, is a behavioural analysis module, courtesy of the company's acquisition of Sana in January.

The new module is called Identity Protection - a misleading name, since it aims to detect all types of malware, with no particular focus on ID theft. It works by looking not at signatures, but at factors such as whether a process is signed, whether it spawns other processes, and whether it acts as a network server.

Naturally, if a process looks suspicious it's intercepted automatically, but for the curious or cautious the software will happily show the calculations that have led it to trust or distrust a process - a reassuring feature most behavioural modules omit.

AVG's interface remains clean and simple enough, once you get through the slightly confusing firewall configuration

Apart from this new arrival, the main AVG 8.5 application is unchanged from its forebear. The main interface remains clean and simple enough, once you get through the slightly confusing firewall configuration. And you still get the web-based protection that impressed us in our last Labs round-up, plus email integration, anti-spam and most of the standard modules, although there's nothing fancy like parental controls or a backup agent.

On the flipside, the browser plug-ins are still cheapened by an irritating Yahoo search box, which can't be closed without hiding the AVG toolbar. And the behavioural analysis module feels distinctly tacked on: it doesn't work on Windows 2000 or 64-bit XP, it insists on placing a second icon in your System Tray, and it isn't accessible from the main AVG interface at all, instead employing its own console. Since the entire raison d'être of this release is to bring Sana's technology into the suite, such poor integration looks a little slapdash.

AVG's web filters are second to none. And its new behavioural module should give it an edge against never-before-seen threats

The addition of the new module also leaves the suite feeling distinctly bulky. This month, we've upgraded our test machine to a Core i7-920 with 3GB of DDR3 RAM, but with AVG Internet Security 8.5 installed it still took 31 seconds to boot to the desktop, plus a further 21 seconds of CPU churning over the next two minutes, settling down to a total RAM footprint of 718MB. For comparison, our new A-Listed favourite Avira Premium Security Suite (see PC Authority July 2009) booted in just 24 seconds, with 14 seconds of post-desktop activity and RAM consumption of 582MB.

In terms of straightforward malware detection, though, AVG 8.5 trails only slightly behind Avira, identifying 94% of our in-the-wild malware samples, while Avira managed to spot 96%. To AVG's particular credit, it identified one sample - a Bravix trojan dropper - that Avira overlooked.

While AVG doesn't quite take the gold in that test, we've noted in the past that its web filters are second to none. And its new behavioural module should give it an edge against brand-new, never-before-seen threats - although that's all but impossible to test realistically.

We hope to see Sana's behavioural technology more fully assimilated into the next version of the suite, since this half-way release would benefit from a little streamlining. But on the whole, AVG's is a credible security suite that's definitely on the up.