A very well engineered game.
I love how you restricted the characters' area limits, making it more of a challenging yet also flexible game. The program upgrades for your arsenal are a nice addition, as in any Tower Defense game is.
But also...this reminds me of one of my favorite RTS-themed games, which is Spybot: The Nightfall Incident. I used to play that all the time when I was young... How you made the network of sites that you must hack and defend is that one element that made me feel that way.
Anyway, I love this game. It's really unique as far as I am concerned. Keep it up, bro!