Kernel 7

[+] Secure ISC BIND Template:
http://www.cymru.com/Documents/secure-bind-template.html

[+] Secure BGP Template for Cisco Routers:
http://www.cymru.com/Documents/secure-bgp-template.html

[+] Secure BGP Template for Juniper Routers:
http://www.cymru.com/gillsr/documents/junos-bgp-template.pdf

[+] Secure IOS Template:
http://www.cymru.com/Documents/secure-ios-template.html
http://wiki.nil.com/Router_security_template

[+] Secure JunOS Template:
http://www.cymru.com/gillsr/documents/junos-template.pdf

If you would like to block an entire country from accessing a service, you can get the entire list from the following IPTables Country BlackList Generator:

http://blacklist.linuxadmin.org/

To reduce the risk of being scanned by script kiddies, tell you system to ignore ICMP ECHO Packets (PINGs):

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all