Source: http://www.cccamforum.com/forums/showthread.php?t=71503

Add this in oscam [reader] section (oscam.server file):

blockemm-u = 1
blockemm-s = 1
blockemm-g = 1
blockemm-unknown = 1

With this config you block all EMMs! This is useful with Sky Italia cards and other providers that send killer EMMs. EDIT: These lines do not help anymore because Sky Italia uses unknown method of killing cards (9995 error for example).

If you want to block global and unknown EMMs (they can flood your card and it is recommended to block them) and still allow unique and shared EMMs use this:

blockemm-u = 0
blockemm-s = 0
blockemm-g = 1
blockemm-unknown = 1

Here is example for Sky Italia:

blockemm-unknown = 1
blockemm-u = 1
blockemm-s = 1
blockemm-g = 1
blocknano = all
audisabled = 1
blockemm-bylen = 183,81