Remote administration of Windows (and helping users)

I need a tool which allows to take controll of user keyboard and/or mouse with support of Linux client (preferably on FLOSS license). It should ask the user about permission (I don't want to give a free troyan crackers). The NAT is not a problem - I have VPN. It should be able to work with lower resolution on client.

Windows is Vista (both 32 and 64 bit editions).

Does anyone know such client?

(By client I mean the connecting computer and by server I mean the Windows machine).

Solution 1:

VNC. Many of the other products will not have great support for Linux as the client.

Solution 2:

I would generally recommend against VNC in a corporate environment. If you're providing support for friends/family or for small mom & pop shops it may be fine. However, most versions of VNC store the password to connect in an easily decryptable form in a known place in the registry for a Windows system. So auditors jump on it. Some of the VNC solutions, like UltraVNC, can do domain authentication (and you should if that's an option). The other issue is that not all VNC products encrypt the session. UltraVNC can, because we used to do so using the AES plug-in.

Solution 3:

At the helpdesk at my university, we use a commercial product called Bomgar. Though it is far from free, Bomgar does have support for Windows, Mac, and Linux in the Representative Console as well as the client and even has a number of diagnostic features (e.g. a process listing). We haven't had any trouble going through NAT, since the client application contacts an intermediary server. In our specific implementation, we do not take control of the user's computer, though I believe Bomgar does support that feature.