Hi,
For all my fellow BAN pool miners that are using Antminer S2s, I thought I'd give you a heads up on a couple of things we were talking about in the IRC chat over this past weekend.
The default firmware file leaves an open security hole for folks to exploit, and hijack your miner to work for them. So far, this has happened to me, with a miner using the name "benutzer" (German for "user"... apropos, right?) at BTC Guild. I don't blame BTC Guild for this one bad apple, but I did try to appeal to them to drop this guy. I don't think I made any progress on that part. I'm sure that they might be good people, with one bad apple.
Well, what I found was a firmware file that was not from Bitmain, but specific for the S2, initramfs.bin.SD-Kano-20140611145346.tar... Avoid it!!! I tried it, and I had 60 million invalid shares in just a moment. What a mess!!!

If your miners are not behind a firewall, for now, all I can advise is that for you to make sure /etc/cgminer.conf.factory has api-allow set as something like this:
"api-allow": "W:127.0.0.1,R:0/0",
It allows you to modify the configurations locally, or via the web interface.
This isn't really a BAN issue. The default S1/2 cgminer has this bug. For anyone who buys an Antminer S1-3, I would recommend updating to the most recent firmware from Antminer directly, and then Kano's actual firmware. I've linked them below.
You can search through this forum for postings by Kano himself mentioning his own firmware to verify.
Kano's CGminer actually fixes this bug, but there are some people who have posted
firmware to scam people out of their mining.