Net::SIP::Dropper3pm

    use Net::SIP::Dropper::ByIPPort;
    my $drop_by_ipport = Net::SIP::Dropper::ByIPPort->new(
        database => '/path/to/database.drop',
        methods => [ 'REGISTER', '...', '' ],
        attempts => 10,
        interval => 60,
    );
    use Net::SIP::Dropper::ByField;
    my $drop_by_field = Net::SIP::Dropper::ByField->new(
        methods => [ 'REGISTER', '...', '' ],
        'From' => qr/sip(?:vicious|sscuser)/,
        'User-Agent' => qr/^friendly-scanner$/,
    );
    my $drop_subscribe = sub {
        my ($packet,$leg,$from) = @_;
        # drop all subscribe requests and responses
        return $packet->method eq 'SUBSCRIBE' ? 1:0;
    };
    my $dropper = Net::SIP::Dropper->new(
        cbs => [ $drop_by_ipport, $drop_by_field, $drop_subscribe ]);
    my $chain = Net::SIP::ReceiveChain->new(
        [ $dropper, ... ]
    );