A deluge of precisely targeted spam designed to harvest intellectual property from companies worldwide was launched on 26 June, security experts have revealed.

More than 500 emails were intercepted in a few hours by MessageLabs, a security firm which filters email for around six million inboxes. The company would normally intercept an average of just 10 targeted email attacks a day. 

The emails were addressed to named senior executives, including their job titles, in companies which own high-value intellectual property.

In some cases, emails were even sent to named executives' spouses or dependents in an attempt to compromise home computers.

"This is an attack in an entirely different league to generic virus or spam threats," said Mark Sunner, chief security analyst at MessageLabs.

The emails had an attached Microsoft Word document containing embedded executable code.

When opened, the executable would activate a Trojan component to compromise the victim's computer, enabling a remote party to download information.

Of the 500 emails intercepted by MessageLabs, 11 per cent of the intended recipients were chief executives. Chief information officers accounted for seven per cent and chief financial officers six per cent.

But the largest number, 29 per cent, was aimed at chief investment officers, a role which would handle commercially sensitive information that could affect share prices, such as details of mergers and acquisitions.

This bias has led some security experts to speculate that the attack was related to stock market pump-and-dump spam activity which showed a considerable spike at the same time.