I need to transfer files between two networks which need to be physically isolated for a few months until a beefed up and permanent security solution becomes possible.
The easiest way to do this on a budget consists of using USB keys to transfer files between two laptops, one which is connected on the intranet, the other on the secure network. If course, the "secure" laptop must be stripped to the bone and have an up-to-date Antivirus so it can trap known viruses that are currently in the wild. That won't prevent any new virus from coming in, but there is an urgent business need to transfer these files so there is not much that can be done in the short term.
I'm currently using IronKeys to ensure the integrity of the data, and also to prevent any data theft if a key is ever stolen. However, one must "encourage" end-users to use these keys, else they might end up using whatever key they lay their hands on to prevent having to enter a password.
On Windows XP, there is no way to do USB key filtering based on the key manufacturer. IronKey has a partner named DeviceLock that they suggest, but being a commercial product, it comes with a price. There are many other endpoint security tools that can be purchased to offer similar functionality, too. In my case, I was in a deadline and had missed the opportunity acquire software and charge it to the project, so it was preferable to use something free as a stopgap measure.
This afternoon, I've been making a few tests with USBSecure. It SEEMS to be free. There is no license, but all code is published so it can be tweaked if necessary. USBSecure is simple to configure: define users that use the computer, and whitelist the device IDs that are allowed on the system. I've been making a few tests for an hour or so, and it seems to work correctly. I might come back and give more details later.
Of course, transferring files between two adjacent PCs might look clumsy. But there are a lot of (justified) restrictions on secure control networks. What is sad is that that Stuxnet worked exactly this way, by propagating using USB keys. No matter how much we try to control their usage using endpoint security software, USB keys still remain a vector of infection for secure networks. Better long-term solutions must be done to ensure that any file transferred on a secure network is, indeed, clean. I'll be working on such solutions in 2011-2012.