Privacy per extension

Does anyone know where I can find more info on the privacy database used in Dial() with option P ?
I would like to exclude some extensions from getting calls from some CIDs.

A small patch to dialparties.agi solves the problem:

--- dialparties.agi.old 2009-12-30 13:05:30.000000000 -0800
+++ dialparties.agi     2010-03-21 21:35:46.000000000 -0700
@@ -194,6 +194,15 @@
        }
        $extarray = split( '-', $arg );
        foreach ( $extarray as $k ) {
+               if ($cidnum == $k ) {
+                       debug("Skipping extension $k",3);
+                       continue;
+               }
+               $pcids = $AGI->database_get('PRIVACY', $k);
+               if (strpos($pcids["data"], $cidnum) !== FALSE) {
+                       debug("Skipping extension $k",3);
+                       continue;
+               }
                $ext[] = $k;
                debug("Added extension $k to extension map", 3);
        }

Now I can add CIDs into the database with multiple CIDs per extension, eg:

database put PRIVACY 701 "+17475551234-5416858773-8001231234"
this also avoids calls to originating extension when dialing call groups

This obviously is a FreePBX patch. I simply did not know at the time about all the ingredients involved in an average Asterisk based distro.