Securing Local Logins

Question 1

/etc/nologin

Answer 1

Can be used to display message on console when someone attempts to log in with account using /sbin/nologin shell.

Question 2

usermod

Answer 2

Additional notes.

• L: lock given user.
• e 1: effectively lock account by setting expire date to 1.
• s: assign shell to user.
• U: unlock given user.

Question 3

/etc/passwd

Answer 3

Contains the main account configuration details of the users on system.
Reminder: ::::::

Question 4

/etc/shadow

Answer 4

Stores the encrypted passwords and password age info for the users on system.
! At beginning of password field indicates lock.
Reminder: :::::::

Question 5

xinetd

Answer 5

Super-daemon. Controls access to various network systems, older.

Question 6

/etc/xinetd.conf

Answer 6

Configuration file for xinetd
General logging in syslog format:
Ex: log_type = SYSLOG daemon info.
Access restrictions: include connections per seconds requested and disable time (s), instances, maximum connections for source IP.
Bottom includes configuration file from /etc/xinetd.d

Question 7

/etc/xinetd.d

Answer 7

Contains configuration files for services which xinetd can control.

Question 8

TCP Wrappers

Answer 8

Functionality users a hosts.allow and/or hosts.deny file to determine access to network services. Formatted as
: ALL is an option for both.

Question 9

systemd.socket

Answer 9

Systemd socket unit file used in place of xinetd on modern Linux distros. Type of unit will allow for on-demand activation of network services. TCP Wrappers can be used in conjunction with systemd socket units.