McAfee on Adsheriff:
Distribution
This is not a virus or a trojan. It is detected as a "potentially unwanted program." This is an anti-spyware application claiming to remove unwanted malicious spyware programs but requires paid registration before any issues found can be fixed or any many other features enabled (on access protections, etc.) It creates a shortcut in the Start Menu Startup folder to ensure it is launched and performs a scan at each system startup. In order to clean or delete any elements identified as threats, the software requires you purchase the full version. If any elements are identified during a scan, an "always on top" warning window appears which cannot be dismissed without pressing the "Register" button, which opens a new browser window to the purchase page for the software. Additionally, neither AdwareSheriff buttons on the task bar (for the main application or the alert window) may be closed via right-click -> Close in the context menu (the menu simply doesn't appear).
More at the link:
http://us.mcafee.com/virusInfo/default.asp?id=description&virus_k=138377