Kevork Djansezian Getty Images COLUMBIA, S.C. More and more Mac OS X users are falling victim to various adware and spyware infections, though still less so than Microsoft Windows-based computers. 'Adware has become a major issue on all operating systems, regardless of their vendor, mostly because potentially unwanted applications are frequently bundled with very popular freeware programs,' said Catalin Cosoi, chief security strategist at Internet security software maker Bitdefender. Most adware and spyware infections happen when Mac or PC users install computer programs developed by third-party programmers, called 'freeware,' and some examples are video downloaders, file converters or PDF-file generators.

Bitdefender notes one of the most problematic adware applications is one known as Genieo that sometimes rides along with freeware. It's also often installed by unsuspecting users who get it directly from the Israeli-based company's website or on consumer tech sites like cnet.com. After installation on a Mac, Genieo ties the web browser's start page to their own search engine. After users search for something, Genieo then will present 'contextual advertising' as search results, also known as affiliate links (read: search results placement paid to Genieo from advertisers) within the displayed search results.

Granted, every time a computer user conducts a search on Google, a similar contextual advertising search result is presented, though Google clearly marks those as ads. But on a Mac or Windows computer infected with the Genieo adware, information is sent back to Genieo's servers for indexing after every search. Genieo co-founder and CEO Sol Tzvi defended the product on Friday via her blog at www.soltzvi.com, saying their software does not fall into the traditional web browser 'hijacker' category in that they seek approval from users that install their program.

Traditional browser hijacking occurs when browser extensions take over without a user's knowledge, and in the case of Genieo.com's software, users are asked for permission for changes made, the blog said. Tzvi said the intent of their software is to help people get caught up on news pertinent to them in the online world, in an aggregated newsfeed based upon browsing behavior. The CEO went on to state they do not populate with 'contextual advertising,' but do add three display ads on a 'personalized startpage.'

It was unclear how they keep track of a user's online behavior and interests to generate the startpage. Genieo software is still available for download through a number of websites including cnet.com, where it's listed as a 'newsreader' – and where users have given it a low rank of 1 star. Online user support forums at apple.com, reddit.com, Yahoo! Answers and other sites, dating back more than two years, display long threads recounting issues when people try to remove the Genieo software, along with dozens of pleas for help in getting it off a computer.

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Also noted in the forums is users' inability to easily navigate the removal tool provided by Genieo, along with the failure of the tool to remove Genieo's original installations. Vlad Valceanu, head of development at Romania-based Bitdefender, said the company's research also turned up numerous posts regarding the failure of the removal tool provided by Genieo. Bitdefender makes a free Mac OS X adware removal tool that will detect and remove all elements of Genieo and restore the web browser settings. Tzvi said by email Friday that Genieo would release a better uninstaller in a few weeks.

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'We have millions of users that use Genieo every month. Not all of them love what we do but there are millions that do enjoy the benefit of our technology,' she said. 'I can assure you that we will continue to improve ourselves and listen to all (of) those feedbacks.'