The latest for me was FoxIt Reader which tries to install Conduit Search "Protect" if you do the standard install (which is why I almost always choose custom/advanced install for everything).
This is the 2nd or 3rd PDF reader/printer that I've had that start out as great products, then, for whatever reason (desperation?) they start adding unwanted payloads to their installs/upgrades but most users will not be aware of until weeks or months later after their PCs have been completely rendered useless by these Trojan Horses.
Some others I've ran across (and actually got by my keen eye and installed):
- Babylon Search (got installed with a "free" SQL tool that was recommended by other SQL professionals at a conference I was at)
- payload.sidekick.net - A re-direct "virus" which was added silently to the iHeartRadio Chrome Extension Both of these were a pain to remove/clean from my PC.
Babylon kept re-installing every time I launched the SQL tool until I realized what program was actually doing this.
Almost makes me long for the days of MS-DOS and green screens... sigh.
Bleeping Computer is a great resource for finding out how to remove these nasty things but beware that many of the solutions are not for the faint of heart and require some patience and attention to detail and a lot of reading to see what works and what doesn't. Here is a place to start: http://www.bleepingcomputer.com/tutorials/how-to-remove-a-trojan-virus-worm-or-malware/
Feel free to share your "free" software horror stories in the comments section.