yes, your talking about stuff like iptables settings - it's important you mentioned this, I just looked up an old post on how to install bitcoind on the pi and I can instantly see that they haven't covered everything - um, like turning on apt-get automatic security updates and turning IPv6 off, and there is other stuff - I can list some bullet points... I haven't looked into pi vulnerabilities for a while - but to be honest debian is made using 'C' so it will always be vulnerable (at some level), there is also the physical security as it's easier to steal, and I for one don't use Wifi ever, but I expect most users do these days (STOP IT) - can't help with that...