We recently received a proof-of-concept sample of an adware program. Normally that wouldn't be worth blogging about, but in this case it's for Mac OS X. In theory, this program could be silently installed to your User account and hooked to each application you use… and it doesn't require Administrator rights to do so. We won't disclose the exact technique used here, it's a feature not a bug, but let's just say that installing a System Library shouldn't be allowed without prompting the user. Especially as it only requires Copy permissions. An Admin could install this globally to all users.
The result: This particular sample successfully launched the Mac's Web browser when we used any of a number of applications.
This is easier to do than with Windows. After all, it's a Mac.