Adobe has replaced Microsoft as the hackers' primary target when trying to infect or take control of PCs. Its software, Flash for Web video and Reader for documents, is loaded on virtually every personal computer.

"As Microsoft has toughened up its securiy, Adobe has become a more tempting prey", explains Business Week in its last issue.

So far this year, Adobe has released nine security updates for the current version of its Acrobat Reader software, up from four in 2008.

"More than a dozen sites, including those of The New York Times, USA Today and Nature, have been infected with fake ads that exploit Adobe software. In the case of the Times, if Web surfers clicked on an ad for antivirus software, malicious code would take control of their computers through Flash and direct them to a site infested with malware. Other attacks circulate via e-mail, with virus-laden PDF files that open in Acrobat Reader," reports Business Week.

It is said that Adobe lacks the resources to stop the attacks, despite its growing attention to security.

Also Yahoo's instant messenger and Apple's iPhone are starting to see attacks.