IPtables VS TCPwrapper VS SSHD config VS /etc/security/access.conf VS PAM

Q.
In how many ways, you can restrict a user to accesss a linux system ?
In how many ways, you can restrict an IP to accesss a linux system ?

Solution:
1. Using IPtables
2. Using TCPwrapper
3. SSH conf file
4. /etc/security/access.conf file