Command manuals for security

AppArmor - kernel enhancement to confine programs to a limited set of resources.

cryptsetup - utility for configuring and managing encrypted storage devices

gpg - OpenPGP encryption and signing tool

iptables/ip6tables — administration tool for IPv4/IPv6 packet filtering and NAT

openssl - OpenSSL command line program

pam - Netpbm common 2-dimensional bitmap format

scp — OpenSSH secure file copy

sftp — OpenSSH secure file transfer

ssh — OpenSSH remote login client

sshd — OpenSSH daemon