Researchers from the company Malwarebytes, which deals with the creation of anti-malware programs, discovered a threat in OS X a few days ago that an inexperienced user might not have discovered. The malware redirects users to a fraudulent page that forces them to download unwanted software that could harm their computer.
Malwarebytes' lead researcher, Thomas Reed, announced that he discovered malware on a fraudulent page hosted on the official Adv website.anced Mac Cleaner. Malware relies on user inattention when installing Advanced Mac Cleaner, which installs and works fine, but also installs a second program called Mac File Opener.
This second program seemed harmless. But after a bit of research, Thomas Reed discovered that the program's Info.plist file defined a list of 232 different file types that it appeared to be able to open. However, if the user tried to open a file for which they did not have a corresponding application installed, it opened in Mac File Opener, which displayed a fake dialog from OS X saying that no corresponding application was installed to open the file.
The fake window links to macfileopener.com which downloads other unwanted PCVARK applications (Mac Adware Remover or Mac Space Reviver). All these applications have valid Apple certificate, so OS X will install them without problems. It would be advisable to warn users that they should be careful what they install on their devices and avoid dubious programs that can do more harm than good.
Source: 9to5mac
but this is already quite scary... and considering that some have online banking on their Mac..
In most cases, just use the most current version of the system and there should be no danger.
It's kind of going downhill with Apple systems…. :/