How would I harden the security of a Linux system using an ansible playbook?
user
There are multiple tasks involved to harden the security, a few general steps to follow:

1. Update the system with the latest security patches and updates

2. Making sure the firewall is on. A lot of turn it off for testing and forget to switch it on

3. Configure the SSH daemon using key-based authentication and disabling root login

4. Enforce strict password policies

5. Enable SELinux and configure it to enforce policies that restrict access to system resources

6. Install and configure intrusion detection tools like fail2ban or tripwire to detect and prevent intrusion attempts

7. Configure system logging to track and monitor events. And remember to look back into the log from time to time
assistant
Could you show me how to configure the SSH daemon using key-based authentication? Please include a good default configuration to use as a starting point.
user
Firstly, you will need to generate a public and private key pair. You can do that by running the following command:
`ssh-keygen`
This will provide you with a public and private key file. You can give out your public key to servers you want to connect to so that you can be whitelisted by them. Your private key should not be shared with anyone as you use it to prove your identity, and someone with your private key can pretend to be you.

In order to be able to connect to your server you need to add your public key to the servers list of authorized ones. Append the contents of id_rsa.pub (The public key) to your server's ~/.ssh/authorized_keys file. Create it if it doesn't exist.

You can transfer your public key to your server via ssh authenticating using your password (SCP, SFTP).

These are the changes you will want to make to your sshd_config file:
```
PubkeyAuthentication yes
PasswordAuthentication no 
PermitRootLogin no
```
The rest of the default configuration file should suffice for these specifications but you can look online on how to further harden your ssh config.
assistant