Cis Ubuntu2004 V300 6 3 3 3

---
name: cis-ubuntu2004-v300-6-3-3-3
description: "Ensure events that modify the sudo log file are collected"
category: cis-logging
version: "3.0.0"
author: cyberstrike-official
tags: [cis, ubuntu, linux, ubuntu-20.04, auditing, auditd]
cis_id: "6.3.3.3"
cis_benchmark: "CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0"
tech_stack: [ubuntu, linux]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# 6.3.3.3 Ensure events that modify the sudo log file are collected (Automated)

## Profile

- Level 2 - Server
- Level 2 - Workstation

## Description

Monitor the `sudo` log file. If the system has been properly configured to disable the use of the `su` command and force all administrators to have to log in first and then use `sudo` to execute privileged commands, then all administrator commands will be logged to `/var/log/sudo.log`. Any time a command is executed, an audit event will be triggered as the `/var/log/sudo.log` file will be opened for write and the executed administration command will be written to the log.

## Rationale

Changes in `/var/log/sudo.log` indicate that an administrator has executed a command or the log file itself has been tampered with. Administrators will want to correlate the events written to the audit trail with the records written to `/var/log/sudo.log` to verify if unauthorized commands have been executed.

## Audit Procedure

### Command Line

Note: This recommendation requires that the sudo logfile is configured. See guidance provided in the recommendation "Ensure sudo log file exists".

On disk configuration - Run the following command to check the on disk rules:

```bash
# {
SUDO_LOG_FILE=$(grep -r logfile /etc/sudoers* | sed -e 's/.*logfile=//;s/,? .*//' -e 's/"//g' -e 's|/|\\\/|g')
[ -n "${SUDO_LOG_FILE}" ] && awk "/^ *-w/ \
&&/"${SUDO_LOG_FILE}"/ \
&&/ +-p *wa/ \
&&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \
|| printf "ERROR: Variable 'SUDO_LOG_FILE' is unset.\n"
}
```

Verify output of matches:

```
-w /var/log/sudo.log -p wa -k sudo_log_file
```

Running configuration - Run the following command to check loaded rules:

```bash
# {
SUDO_LOG_FILE=$(grep -r logfile /etc/sudoers* | sed -e 's/.*logfile=//;s/,? .*//' -e 's/"//g' -e 's|/|\\\/|g')
[ -n "${SUDO_LOG_FILE}" ] && auditctl -l | awk "/^ *-w/ \
&&/"${SUDO_LOG_FILE}"/ \
&&/ +-p *wa/ \
&&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \
|| printf "ERROR: Variable 'SUDO_LOG_FILE' is unset.\n"
}
```

Verify output matches:

```
-w /var/log/sudo.log -p wa -k sudo_log_file
```

## Expected Result

Both on disk and running configuration should show a watch rule on the sudo log file.

## Remediation

### Command Line

Note: This recommendation requires that the sudo logfile is configured. See guidance provided in the recommendation "Ensure sudo log file exists".

Edit or create a file in the `/etc/audit/rules.d/` directory, ending in `.rules` extension, with the relevant rules to monitor events that modify the sudo log file.

Example:

```bash
# {
SUDO_LOG_FILE=$(grep -r logfile /etc/sudoers* | sed -e 's/.*logfile=//;s/,? .*//' -e 's/"//g')
[ -n "${SUDO_LOG_FILE}" ] && printf "
-w ${SUDO_LOG_FILE} -p wa -k sudo_log_file
" >> /etc/audit/rules.d/50-sudo.rules || printf "ERROR: Variable 'SUDO_LOG_FILE' is unset.\n"
}
```

Merge and load the rules into active configuration:

```bash
# augenrules --load
```

Check if reboot is required:

```bash
# if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi
```

## References

1. NIST SP 800-53 Rev. 5: AU-3

## CIS Controls

| Controls Version | Control                                                        | IG 1 | IG 2 | IG 3 |
| ---------------- | -------------------------------------------------------------- | ---- | ---- | ---- |
| v8               | 8.5 Collect Detailed Audit Logs                                |      | X    | X    |
| v7               | 4.9 Log and Alert on Unsuccessful Administrative Account Login |      | X    | X    |

MITRE ATT&CK Mappings: T1562, T1562.006 / TA0004