Further to other replies:
Bittorrent ("torrents") is a perfectly legitimate way of distributing files over the internet - just like FTP, HTTP (i.e. regular web downloads), email attachments etc. all of which can be used to distribute legitimate files/software or pirated stuff infested with malware.
The issue is the trustworthiness of the source - not the download method. Look for sites that are linked from other reputable sources, preferably more than one, do the research, try and find the site of the original author rather than some odd download site.
If you're invited to first install their super fast download utility (adware at best), or if the actual download link is hidden away below lots of big green fake DOWNLOAD some random bit of junkware buttons, then just walk away (some of those sites are actually legit, but they don't deserve anybody's clicks).
And, yeah, that first Flash player window is as fake as a $9 bill - and the only way to be sure that the second one isn't just a good fake by someone who can write English is to download it from Adobe's own site.
NB: The Mac is less prone to viruses than Windows (esp. past versions of windows) but that mainly refers to self-spreading viruses rather than "trojans" that trick you in to running or installing them manually.