[this post from Dennis Houseknecht]
Most of us know and love Ccleaner as a cleanup tool with a value-packed FREE version. Be aware, though, that there is a not-so-free fake version out there as well.
Another tool many of us use is Ad-aware from Lavasoft. Fake versions abound. This is example of how rogue programs trick users into installing them.
Here is fake love test app for Android that is really malicious software.
Finally, here is a trojan downloader pretending to be a FireFox update.
It’s important to be aware of which programs you’re downloading and using. Make sure you’re only downloading software from reputable websites. Downloading directly from the official company website is best. Some programs are free, and some are not, so do your research. There are many malicious programs out there that look very similar to commonly used programs, but in fact are malicious. If you’re unsure, ask a Nerd!