ISOs for Linux Mint 17.3 been hacked as of Feb. 20th ? That is my question
 

I have just installed the Linux Mint 17.3 and I received a message that it had been hacked. I am new to this program so I don't know if this is true or if it effects my security.

How did you receive that message ?.
The Cinnamon iso was the only one affected - and only for one day. Readthis blog, and md5sum check your iso as it mentions. If your md5 agrees with what is published on the blog you are ok. If not, do as it says and re-download and re-install.

Good luck.