Change all of the default ports, turn off or remove all of the built in accounts, you can't shut off "admin" but change the default password. You don't need to run port 80 to access your device over the web. Just by doing these small things you can greatly increase the security of the DVR. Make sure you are running a good router firewall (you can disable UPnP, this should stop the dvr from adding any forwards to your router). DO NOT put any device on DMZ, ever. One of the biggest security risks is people running default configurations on well known devices.
It seems my directv dvr opens and forwards more ports then anything else. Well, it used to but I don't use the DirecTV APPs so it's off.
If you are running wireless access make sure you have the access restriction set allow only the MAC addresses you input. Run WAP2 personal with AES encryption and use a lengthly generated password.
You can check out this forum. There seems to be some really smart guys there. They do seem a little bias on the cheaper costco and bestbuy bundles but they do have great info on why. Seems there is a some what high failure rate.
I did get a package deal from security camera king but wished I had not. The DVRs are top notch. I pick up this one.
It's a little less expensive because it doesn't have a dvd burner in it. I didn't need one. In my previous post I mentioned these are made by http://www.dahuasecurity.com/
which from my readings is a very high end company in surveillance gear.
I used the build a system with security camera king and pick up 4 cameras. Two of their base cameras(they have no control over their features) and couple of outside dome cameras(these do have adjustments for lens/shutter). After Jim's recommendation I pick up two Digital watchdogs. With noise reduction and the street light I can even get color video at night. Without adjusting the DWD cameras I can see they are very nice. Once I get the camera picture adjusted on all of them I'll upload some photos.