cis-ubuntu1204-v110-8-1-11

name	cis-ubuntu1204-v110-8-1-11
description	Collect Unsuccessful Unauthorized Access Attempts to Files
category	cis-os-hardening
version	1.1.0
author	cyberstrike-official
tags	["cis","ubuntu",12.04,"linux","logging","auditd","access","unauthorized","eacces","eperm"]
cis_id	8.1.11
cis_benchmark	CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

8.1.11 Collect Unsuccessful Unauthorized Access Attempts to Files (Scored)

Profile Applicability

• Level 2

Description

Monitor for unsuccessful attempts to access files. The parameters below are associated with system calls that control creation (creat), opening (open, openat) and truncation (truncate, ftruncate) of files. An audit log record will only be written if the user is a nonprivileged user (auid >= 500), is not a Daemon event (auid=4294967295) and if the system call returned EACCES (permission denied to the file) or EPERM (some other permanent error associated with the specific system call). All audit records will be tagged with the identifier "access."

Rationale

Failed attempts to open, create or truncate files could be an indication that an individual or process is trying to gain unauthorized access to the system.

Audit Procedure

Using Command Line

On 64 bit systems, perform the following command and ensure the output is as shown to determine if there are unsuccessful attempts to access files:

grep access /etc/audit/audit.rules

On 32 bit systems:

grep access /etc/audit/audit.rules

Expected Result

For 64 bit systems:

-a always,exit -F arch=b64 -S creat -S open -S openat -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b64 -S creat -S open -S openat -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access

For 32 bit systems:

-a always,exit -F arch=b32 -S creat -S open -S openat -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access

Remediation

Using Command Line

For 64 bit systems, add the following lines to the /etc/audit/audit.rules file:

-a always,exit -F arch=b64 -S creat -S open -S openat -S truncate -S ftruncate -F =-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always, -F =b32 -S creat -S open -S openat -S  -S ftruncate -F =-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always, -F =b64 -S creat -S open -S openat -S  -S ftruncate -F =-EPERM -F auid>=500 -F auid!=4294967295 -k access
-a always, -F =b32 -S creat -S open -S openat -S  -S ftruncate -F =-EPERM -F auid>=500 -F auid!=4294967295 -k access

pkill -HUP -P 1 auditd