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CIS Ubuntu 14.04 LTS - 1.1.20 Ensure sticky bit is set on all world-writable directories

DevOps & Security
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Ensure sticky bit is set on all world-writable directories to prevent unauthorized file deletion

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_14.04_LTS_Benchmark_v2.1.0/cis-ubuntu1404-v210-1-1-20/SKILL.md

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1.1.20 Ensure sticky bit is set on all world-writable directories (Scored)

Profile Applicability

  • Level 1 - Server
  • Level 1 - Workstation

Description

Setting the sticky bit on world writable directories prevents users from deleting or renaming files in that directory that are not owned by them.

Rationale

This feature prevents the ability to delete or rename files in world writable directories (such as /tmp) that are owned by another user.

Audit Procedure

# Run the following command to verify no world writable directories exist
# without the sticky bit set:
df --local -P | awk {'if (NR!=1) print $6'} | xargs -I '{}' find '{}' -xdev -type d \( -perm -0002 -a ! -perm -1000 \) 2>/dev/null
# No output should be returned.

Expected Result

No output should be returned. Any output indicates world-writable directories without the sticky bit set.

Remediation

# Run the following command to set the sticky bit on all world writable directories:
df --local -P | awk {'if (NR!=1) print $6'} | xargs -I '{}' find '{}' -xdev -type d -perm -0002 2>/dev/null | xargs chmod a+t

Default Value

By default, not all world-writable directories have the sticky bit set.

Notes

Some distributions may not support the --local option to df.

References

  • CIS Ubuntu Linux 14.04 LTS Benchmark v2.1.0
  • CIS Controls: 13 Data Protection

Profile

  • Level 1