It is allegedly a Trojan horse virus, hidden inside adware created by the website Twistedhumor.com. It is downloaded onto your computer if you use the online game Yo Mama Osama ' where you try to shoot Osama Bin Laden. It apparently monitors your Internet usage and feeds pop-up ads everytime you go online. It will download files onto your PC, if you do a search these should be under the following names: WNAD.EXE, WNAD.DAT, WNAD-UPDATE.EXE and WNAD.LGC. These files are placed in the Windows folder and a shortcut to WNAD.EXE is added to the Startup folder.
If you remove the game from your PC the virus will remain, so it has to be removed manually. To do this follow the following instructions:
1. Press CTRL-ALT-DEL and use End Task to close WNAD.EXE
2. Go to your Windows folder and delete WNAD.EXE, WNAD.DAT, WNAD-UPDATE.EXE and WNAD.LGC
3. Remove the C:\Windows\Wnad.exe value from the following Registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
4. Delete the shortcut for WNAD.EXE from the Start | Programs | Startup Folder
Good luck!