cis-ubuntu2004-v300-2-4-1-8

DevOps & Security

Ensure access to /etc/cron.d is configured

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_20.04_LTS_Benchmark_v3.0.0/cis-ubuntu2004-v300-2-4-1-8/SKILL.md

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Ensure access to /etc/cron.d is configured

Profile

Level 1 - Server
Level 1 - Workstation

Description

The /etc/cron.d directory contains system cron jobs that need to run in a similar manner to the hourly, daily weekly and monthly jobs from /etc/crontab, but require more granular control as to when they run. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory.

Rationale

Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls.

Audit

IF - cron is installed on the system:

Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other:

Command Line

# stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.d/

Output:

Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root)

Note: If the directory does not exist, this is considered a passing state.

Remediation

IF - cron is installed on the system:

Run the following commands to set ownership and permissions on the /etc/cron.d directory:

Command Line

# chown root:root /etc/cron.d/
# chmod og-rwx /etc/cron.d/

Default Value

Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)

References

NIST SP 800-53 Rev. 5: AC-3. MP-2

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.3 Configure Data Access Control ListsConfigure data access control lists based on a user's need to know. Apply data access control lists, also known as access permissions, to local and remote file systems, databases, and applications.	●	●	●
v7	14.6 Protect Information through Access Control ListsProtect all information stored on systems with file system, network share, claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the information based on their need to access the information as a part of their responsibilities.	●	●	●

MITRE ATT&CK Mappings

Techniques / Sub-techniques	Tactics	Mitigations
T1053, T1053.003	TA0002, TA0007	M1018