[drinchev]

Can someone explain how the vicim gets infected?

As far as I can read from the article they discuss what happens if you are infected.

Also, isn't running binary files on OS X from let's say "Finder" automatically triggers Security alert ( like App-vendor lock )?

[alexbecker]

This isn't a virus, it's a payload. Once an attacker exploits a vulnerability to gain RCE, this is the kind of thing they might install (if their goal isn't to immediately trash the machine).