The last quarter of 2004 was categorised by a distinct trend of virus writers moving away from merely trying to create disruptions to developing malicious code that could potentially generate revenue.

According to the Q4 Web Security Threat Report from ScanSafe, the end of last year witnessed a rise of 13 per cent in the total number of attacks, which in turn reflected an increase in spyware of 15 per cent over the same quarter.

Spyware was most commonly seen as standalone programs that can be unwittingly downloaded by users to secretly monitor system activity such as detecting passwords, Pins and other confidential information.

The results of the analysis also showed an increase in the emergence of adware. According to the security firm, this stealth code now accounts for three of the top 10 most prolific threats recorded and 8.2 per cent of all web threats.

"The increase of stealth code such as spyware and adware should be taken as a warning across industries," said Roy Tuvey, chief executive at ScanSafe.

"Virus writers are not just interested in destroying systems and knocking out websites anymore. They are beginning to realise that they can make serious money from harvesting confidential personal information and selling it to spammers or those involved in organised crime and fraud."

The virus activity in the fourth quarter included a multitude of newly developed browser vulnerabilities aimed not only at Internet Explorer, but at the more recently released open source browser, Mozilla Firefox.

This included a potentially devastating website dialog spoof that enabled virus writers to convince users that they were viewing a genuine site, when in fact they were accessing a page created by the attacker.

The study indicated a 17 per cent increase in the number of different types of web threat in the wild that has led to ScanSafe's managed security service now blocking at least one threat per user per month.

"We can see that yet again there are more attacks, more varied threats and new motivation for virus writers to spend their time creating this software," said John Edwards, chief technology officer at ScanSafe.