Sometimes, the simplest ideas can be the most effective. Star Technology Group may be a case in point.

Maintaining anti-virus software on every PC that connects to an organisation's network can be an awkward, time-consuming business. Instead, Star offers an outsourced virus scanning service, so that incoming email can be examined for viruses before it hits the corporate mail server, let alone the desktop PCs of end-users.

The service was launched in July 1999 and proved to be an instant hit, not just among Star's core customers, but with major multinationals and, increasingly, from companies in the US as well. By January 2000, Star had set-up MessageLabs as a separate unit to focus on the anti-virus service, as well as offering an increasing range of content filtering services, such as scanning for spam and pornographic images.

Today, MessageLabs boasts about one million end-users on four continents, no doubt attracted by MessageLabs' claim that it has not let one virus slip through its net in almost three years of operation, according to co-founder and marketing director Jos White.

It has achieved this, says White, by deploying not one, but four anti-virus scanners. Off the shelf, it uses anti-virus software products from McAfee, F-Secure and VFind from Cybersoft. This is augmented by Skeptic, its anti-virus engine.

Skeptic's strength is its heuristics engine. This is a technology for examining incoming email attachments and assessing their ability to do harm to an end-users PC, based on a collection of rules, such as whether it contains Visual Basic Script or needs to access the user's email address book – both clear signs of nefarious intent.

Heuristics enables MessageLabs to block viruses before traditional anti-virus software vendors have examined new viruses and issued a ‘signature' to enable their software to identify it.

The success of the email scanning service has helped the company to raise £35 million (€57.3m) in two rounds of venture capital. And, says White, the company is now close to profitability and growing fast. In the year to the end of July 2001, the company posted revenues of £16.7 million (€27.4m), which is forecast to more than double to £36 million (€59m) in the current fiscal year. MessageLabs will account for about £7 million (€11.5m) of that total.

A public flotation is being considered before the end of the year. But the company will need to move fast to consolidate its position. Anti-virus software vendors have not only started to build heuristic capabilities into their software, they are also starting to offer managed email filtering services themselves.