• April 3, 2009

The number of Web sites blocked worldwide by security applications for hosting malicious code and content rose by 197.2% to 2,797 sites per day in March, the highest level since October 2008, according to MessageLabs Intelligence.

A sharp increase in the number of images hosted on Web sites and embedded in emails, which contain injected scripts such as JavaScript or VBScript, contributed to the rise, the company said.

The technique used by hackers appears as an attempt to exploit a flaw in older browsers where HTML, JavaScript or VBScript is attached to the end of the image code. JavaScript, typically used to invisibly serve up online ads, has also been used with a variety of free online tracking tools, where tracker codes are relied on to monitor visitors to specific Web pages.--Laurie Sullivan