You can use https://aka.ms/ms12-020 to read up on the latest news related to the RDP security update that came out today.
A more in-depth technical writeup about the update can be accessed here, which also includes a few FixIt items that can enable Network Layer Authentication (NLA) for RDP connections.
One FixIt to enable NLA. One FixIt to disable NLA. One FixIt to enable NLA support for Windows XP SP3.
Enabling NLA, in general, is a good idea anyway and I've always configured my PCs to use it ever since Windows Vista.
With NLA, the user connecting in will need to have proper user credentials before the server creates a full blown RDP session.
From what I can tell, the files updated in this security release, for Windows 7, are rdpcore.dll and rdpcorets.dll.