The Ubuntu operating system default filesystem permissions must be defined in such a way that all authenticated users can read and modify only their own files.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-238209	SRG-OS-000480-GPOS-00228	UBTU-20-010016	SV-238209r991590_rule	2025-03-03	2

Description
Setting the most restrictive default permissions ensures that when new accounts are created they do not have unnecessary access.

ℹ️ Check
Verify the Ubuntu operating system defines default permissions for all authenticated users in such a way that the user can read and modify only their own files. Verify the Ubuntu operating system defines default permissions for all authenticated users with the following command: $ grep -i "umask" /etc/login.defs UMASK 077 If the "UMASK" variable is set to "000", this is a finding with the severity raised to a CAT I. If the value of "UMASK" is not set to "077", is commented out, or is missing completely, this is a finding.

ℹ️ Check

Verify the Ubuntu operating system defines default permissions for all authenticated users in such a way that the user can read and modify only their own files. Verify the Ubuntu operating system defines default permissions for all authenticated users with the following command: $ grep -i "umask" /etc/login.defs UMASK 077 If the "UMASK" variable is set to "000", this is a finding with the severity raised to a CAT I. If the value of "UMASK" is not set to "077", is commented out, or is missing completely, this is a finding.

✔️ Fix
Configure the system to define the default permissions for all authenticated users in such a way that the user can read and modify only their own files. Edit the "UMASK" parameter in the "/etc/login.defs" file to match the example below: UMASK 077