Some Linux fans just got a hard lesson about the importance of double-checking install files. The Linux Mint team is warning users that hackers compromised the ISO (drive image) downloads for 17.3 Cinnamon on February 20th, pointing people toward a modified version with a security backdoor. The intruders broke into the forums, too. You're safe if you grabbed Linux Mint through BitTorrent or a direct web link, and it's easy to both verify if you're affected and install a safe release. Still, the developers aren't taking any chances -- they're keeping the relevant server down until they know everything is in the clear.
Update: You might not have to worry too much if you're a victim. Researchers don't believe the backdoor, an attempted botnet, actually works. Also, this was part of a one-off attempt at making a quick buck (a whopping $85) from selling the forum data, rather than some larger, more sinister scheme.