Do not get too worried. It was the cinnamon versions of Mint 17.3 for one day only, 20th, where downloaded .iso files were 're-routed' via Bulgaria.
AFAIK the problem stems from LM's use of WordPress as a host. So, for the moment their user forum and links to the main downloads page are disabled.
The LM blog says that updates are not affected (most come from ubuntu anyway)
Using LM 17.1 ? must never have updated then

see
http://blog.linuxmint.com/?p=2871 as an example.
Desperate for a LM live DVD? The mirrors are still there, use the MATE versions, use the MD5 checksums, check the issue date (before 20th)
example
https://ftp.heanet.ie/mirrors/linuxmint ... able/17.3/Of course if you
did download last Saturday, and you
have installed it, reformat and start again.
There is a way of checking a DVD, run a 'live' session, look for a file
/var/lib/man.cy, then this is an infected ISO.