According to the McAfee, exploits in Adobe's PDF file format are climbing in 2010. Microsoft said that 46% of browser-based exploits during the latter half of 2009 were aimed at the free PDF reader, while McAfee reports that 28% of all malware is leveraging exploits in the reader. This figure is up from 17% in 2009.
"In the last three years, attackers have found PDF vulnerabilities more and more useful, for a couple of reasons," Dirro said. "First of all, it's increasingly difficult for them to find new vulnerabilities with the operating system and within browsers that they can exploit across the different versions of Windows. And second, Reader is one of the most widely deployed applications that allows files to be accessed or opened within the browser."
One option to avoid these exploits / malware is to use an alternate PDF reader such as the one offered by Foxit which can block many common attack vectors. Learn more about it here and from the company website.
And, according to Spamhaus, the U.S. currently tops the 10 worst spam countries in terms of production and export of spam.