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You may not be aware that this question, like many others, has already been discussed quite a bit (beat to death, actually!) Using MRoogle to search the forums before you post will frequently reveal threads related to your question that the standard forum search misses, and will help you avoid posting repetitive threads. Here are some of the dozens of threads on this topic, filled with opinions and recommendations:
http://www.google.com/search?hl=en&lr=&q=virus+site:forums.macrumors.com&as_qdr=y&btnG=Search

One thread that you may find particularly helpful is this one: https://forums.macrumors.com/showthread.php?p=7066120

By the way, the file you downloaded is a codec file, which can't install on your Mac unless you actively install it and enter your administrator password. Look in your Downloads folder and move it to the Trash.
 
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