what do you mean virus free netbus? NetBus is not a virus, but it is considered to be a trojan. It is also quite widespread and used frequently to steal data and delete files on peoples machines. NetBus is a remote administration tool, much like the infamous Back Orifice tool. However, Netbus predates Back Orifice by several months and is also capable of working under Windows NT in addition to Windows 95 and 98. Contact www.netbus.org if you have questions about the commercial status of Netbus
Beware though, if you put it on someone else's machine, this is illegal! And also the netbus trojan is VERY easy to detect (for AV).
Netbus is "OLD".... I learnt about netbus about 7-8 years ago. AV these days can detect such trojan easily. It is almost difficult to use them without having the administrator of the host (not client) to allow it.