How does MIUI Firewall work?

[Skinjob]

Doing Google search, I can't seem to find anything but very very basic information on the MIUI firewall. It's not obvious, but it seems it can block both SMS and Calls. I would most like to know how to set it to block ONLY SMS messages (and specific phone numbers from voice callers). Can you not tell the program to both accept from the whitelist AND block from the blacklist??

Also, where is "Call Firewall", the 2nd firewall app that blocks apps from the internet? I can't find this in my MIUI 2.4.1.3 ROM?

Thank you in advance!