I know a few of you here (like me), use Linux either as a primary or secondary . Well, our honeymoon is over!
Whereas I never worried about infection to any degree, there is now a significant trojan that will cause you grief if it installs. It's called "Hand of Thief" and written by cyber criminals for criminals and attracts a premium price.
From what I understand, the Linux kernel remains secure. The attack vector for this trojan is via popular browsers. If you remain firmly within the distro repositories for your applications, and downloads, you should remain safe, as there's already a robust review process prior to the updates being included. However, if you install from unknown sources, you could become vulnerable if that source has been compromised.
You can find more about the problem here and here.
Remember, always use a complex password (whatever you're using) and take all the normal sensible steps to prevent infection.