As Wareagle suggests, the RDP protocol is secure, but the authentication process is not quite as secure (at least the last time I checked). There’s a very slight opportunity for a MITM (Man In The Middle) attack. But that would require perfect timing by someone waiting on the same network for the opportunity. So while it’s highly unlikely to present a problem, we can't say it's 100% safe because of this one minor vulnerability.
Frankly, what I strongly recommend to ppl using ANY remote services is to run them over a VPN (SSH is another option but a bit too complicated for the average user, imo). If you use something like Hamachi ( https://secure.logmein.com/US/products/hamachi2/
), you never need to worry about ANYTHING you do over the VPN. It will protect ALL your protocols, whether it's Windows file sharing, RDP, VNC, FTP, HTTP, you name it. And it's incredibly easy to setup and use. You just install Hamachi on your remote desktop machine and laptop. The installer creates a virtual network adapter for each, w/ a unique IP address in the 5.x.x.x network. Finally you JOIN those devices into a named network (of your choosing) and whalla, you can refer to each device by their respective 5.x.x.x IP addresses. And from then on everything you do is transparently secured within the Hamachi VPN. It's a beautiful thing.
Like anything new, at first it might not make sense. But once you “get it”, you’ll wonder why everyone doesn’t use it all the time. And it’s FREE. It’s just awesome. So awesome that I ditched SSH some time ago in favor of it, it’s just easier to use and manage.
Btw, one of the other beauties of Hamachi is that it doesn’t require leaving ports open, or managing ports, at all. Even if your RDP sessions are safe, your open ports are subject to attack. If there are vulnerabilities and hackers discover the service is running, you’re a potential target. Yes, using non-standard ports helps, but relying on “secure through obscurity” is still risky. Also, you typically need to use dynamic DNS services to track your public IP. Hamachi eliminates all these problems. Because it uses a rendezvous server and NAT traversal technology, you never have to open or manage ports or use a dynamic DNS service. The rendezvous server knows where all 5.x.x.x devices are at all times and opens the ports, as necessary, from INSIDE your network! It even addresses the authentication problem w/ RDP since the login is within the VPN as well.
You should try it, I think you’ll like it.