libnetfilter_cthelper: libnetfilter_cthelper (userspace infrastructure for conntrack helpers) libnetfilter_cthelper: libnetfilter_cthelper: Connection tracking helpers allows you to filter multi-flow protocols libnetfilter_cthelper: that usually separate control and data traffic into different flows. libnetfilter_cthelper: This is the case of application protocols like FTP, SIP and H.323 that libnetfilter_cthelper: are already supported by Netfilter. These helpers are implemented in libnetfilter_cthelper: kernel-space. libnetfilter_cthelper: libnetfilter_cthelper: libnetfilter_cthelper: libnetfilter_cthelper: