Linux + CentOS7 1. What are the default firewall rules that are configured in a
ID: 3844842 • Letter: L
Question
Linux + CentOS7
1. What are the default firewall rules that are configured in a CentOS minimal installation?
*What does it block by default?
*What is allowed?
2. Setup a password policy on both systems to enforce the use of complex passwords:
*Password length must be more than 8 characters.
*Password must have a mix of capital and lower case letters.
*Password must have at least 1 number and 1 special character.
*All passwords expire after 30 days and the same password cannot be reused.
*Provide detailed documentation on how you completed this task in your lab report.
3. Install nmap and tcpdump on both systems with yum.
4. Use nmap to probe both systems for open ports.
*Do this with and without the firewall enabled (turn off firewalld).
*What are the differences?
*If ports were found open idenfity what services they belong to.
*Try to figure out how to use nmap to gain more detailed information about the host and open ports while iptables is disabled.
5. On your CentOS1 system run tcpdump and redirect the output to a file so that it can be parsed later.
6. While tcpdump is running (remember backgrounding?) use links on the same machine to surf the web (yum install elinks).
*After you have visited a few pages close links.
*Stop tcpdump and view the output file.
7. What was captured? Be very specific in your writeup, include things like data, ports, protocols, etc…
8. Use tcpdump again but this time filter the output for http traffic only (hint: look at the man page)
Document everything in the lab report and include your configuration files in the document.
Explanation / Answer
First of all assign the dmz zone as the default zone to eth0.
After that add permanent service rules for HTTP and HTTPS to the dmz zone.
Finally Reload FirewallD.
How to setup Setup a password policy on linux
To set minimum password length we need to edit /etc/pam.d/common-password file in the following line
password [success=2 default=ignore] pam_unix.so obscure sha512
by adding minlen=8 at the end.
password [success=2 default=ignore] pam_unix.so obscure sha512 minlen=8
3) yum is nothing but a package installer we can install nmap and tcpdump as follows:
[root@IThelpblog ~]# yum install tcpdump
[root@IThelpblog ~]# yum install nmap
4) By executing the following command it displays a file and it shows open ports:
less /usr/share/nmap/nmap-services
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