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Linux Security

Linux Security. See who's logged in. 1) w     (more information) 2) who     (less information). Disable remote logins for "root" account. 1) Deactivate telnet daemon     sudo service telnet stop 1.5) Remove telnet daemon (unless REALLY needed)     sudo apt-get remove telnetd

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Linux Security

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  1. Linux Security

  2. See who's logged in 1) w     (more information) 2) who     (less information)

  3. Disable remote logins for "root" account 1) Deactivate telnet daemon     sudo service telnet stop 1.5) Remove telnet daemon (unless REALLY needed)     sudo apt-get remove telnetd 2) Disable root logins in ssh server (use nano or vi as root)     edit /etc/ssh/sshd_config; find "PermitRootLogin", set to "no"     Restart ssh: sudo service ssh restart 3) Disable all remote root logins in /etc/security/access.conf     add line to access.conf:     "- : root : ALL EXCEPT LOCAL"

  4. Disable toor account a) Delete the account:     sudo userdel toor b) Disable (Lock) account:     sudo usermod -L toor c) Set toor's login shell to /usr/sbin/nologin:     (edit /etc/passwd; change  last argument on toor's entry to /usr/sbin/nologin)

  5. Enforce Password Length edit /etc/pam.d/common-password (with sudo) Append the first line containing "pam_unix.so" with     min=8 This will enforce a minimum password length of 8 characters. NOTE:     Can be set to any desired minimum length

  6. Create User Accounts sudo useradd -m -G users,development,remote username -m creates home directories -G adds the new user to the listed groups     (users,development,remote)

  7. Check Active Network Service 1) Netstat (IPv4, Listening, show Process name)     sudo netstat -4lp 2) Check the Internet Services daemon     cat /etc/inetd.conf

  8. Check Active Processes 1) ps -ex Show processes for Everything, with eXtended info 2) pstree -a Show process in tree format, with Attributes

  9. End suspect processes 1) kill (PID) Ask the specified process to end nicely 2) kill -15 (PID) Tell the process to end 3) kill -9 (PID) Tell the system to end the process 4) sudo kill -9 (PID) As root, tell the system to end the process

  10. chmod explained chmod: Change file privileges- identity, privilege Identities are     User = u     Group = g     Other = o Privileges are     Read = r     Write = w     Execute = x chmod u+x;  chmod g-w; chmod o-wr

  11. chown explained CHange OWnership, in user:group format. Change /home/development to be owned by root:     chown root: /home/development Change /home/development to be owned by wheel group:     chown :wheel /home/development Change /home/yourfile:     chown you:users /home/yourfile

  12. Create a Shared File Folder Create the folder, give it following permissions:     (group ownership = development)     User, Group, Other: No Execute     Other: No read or write     Group: Read and Write mkdir /home/Development chown -R :development /home/Development chmod ugo-x /home/Development chmod o-rw /home/Development chmod g+rw /home/Development

  13. Log File Analysis Logs are stored in /var/log/ Example:     /var/log/messages    (generic messages)     /var/log/syslog           (kernel messages)     /var/log/auth.log        (Authentication log) auth.log records all login attempts-- local, ssh, telnet, etc.

  14. Reading log files Dump to the screen cat /var/log/auth.log Show entries in scrollable format less /var/log/auth.log Show last 10 entries tail /var/log/auth.log Show last ten entries, and any subsequent entries tail -f /var/log/auth.log

  15. grep logfiles Keyword searches on logfiles: Show login attempts for kdewey: grep 'kdewey' /var/log/auth.log Show sudo uses: grep 'sudo' /var/log/auth.log

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