Building a secure environment for Linux Environment

• How logging in as a root user can land you in trouble 
• Perks of using sudo
• Setting up sudo privileges for full administrative users
• Adding user to a predefined admin group 
• Creating an entry in the sudo policy file
• Assigning limited sudo privileges 
• Enabling and disabling sudo timer
• Check sudo privileges 
• Sudoer file
• Restricting users with having root shell access
• Preventing users from using shell escapes 
• Restricting users from using dangerous programs like text editor or file manipulation
  • cat
  • cut
  • awk
  • sed 
• Restricting the user action with commands 
• Detecting  and deleting default users accounts 
• Enforcing strong password criteria 
• Pluggable Authentication Module
  • Tool used for PAM is pwquality 
• Preventing brute force password attacks 
• Locking user’s account with passwd
• Why take the chance of getting your root account compromised? Locking the root 
• Detecting compromised passwords with https://haveibeenpwned.com 
• Centralized user management 
• Shadow passwords and why they are important 
• Managing and forcing account expiry
• Multi Factor  authentication implementation 
• Using IDS
• Security by account type

• Understanding iptables
• Understanding firewalld
• Blocking ICMP with iptables
• nftables 
• Firewalld for Redhat
  • Firewalld zones
  • Adding services to firewalld zone
  • Adding ports to firewalld zone
  • Using firewalld rich language rules
  • Firewalld commands

• GPG
• Encrypting disk partitions unified key setup 
• Full disk encryption
• Encrypting directories 
• OpenSSL

• Ensuring that SSH protocol is disabled
• Using keys for passwordless login
• Disabling root user login and other users 
• Configuring SSH with strong encryption algorithm 
• System-wide encrypting policies
• White listing, black listing access control and TCP wrappers
• Disabling SSH tunnelling 
• Disabling ICMP tunnelling
• Changing the standard port for SSH
• Managing SSH keys
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• Using chown for editing ownership of files and directories 
• SUID and SGID permissions on regular 
• Extended file attributes to protect sensitive files
• Protecting system configuration files
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• Making ACL for user or groups 
• ACL mask for removing a specific permission 
• Using tar  – – acls  to prevent the loss of ACLs during a backup
• Making Shared Directory 
• ACLs to access file in the shared Directory
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• Setting important access control with SElinux and AppArmor
• Benefits to system admin by using SELinux
• Security context for files and directories 
  • using chcon 
  • using restorecon 
  • using semanage 
    
• Setroubleshoot for Troubleshooting 
• SELinux Policies

• Understanding the /proc filesystem
• Setting kernel parameters with sysctl
• Configuring the sysctl.conf file
• Understanding process isolating
  • cgroups
  • namespace isolation
  • kernel capabilities
  • system calls and SECCOMP

• Scanning Rootkits and rootkit hunter
• Malware analysis with strings and virus total

• Understanding the system log files
• Understanding rsyslog and journald
• Setting remote log server

Vulnerability scanning and IDS

• preventing kernel parameter edits on Redhat
• Securely configuring BIOS/UEFI
• Using a security checklist for system setup