Cis Ubuntu1604 V200 6 2 9

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 6.2.9

Profile

• Level: 1 - Server
• Level: 1 - Workstation
• Assessment Status: Automated

Description

The .forward file specifies an email address to forward the user's mail to.

Rationale

Use of the .forward file poses a security risk in that sensitive data may be inadvertently transferred outside the organization. The .forward file also poses a risk as it can be used to execute commands that may perform unintended actions.

Audit Procedure

Command Line

Run the following script and verify no lines are returned:

#!/bin/bash
awk -F: '($1!~/(root|halt|sync|shutdown)/ &&
$7!~/^(\/usr)?\/sbin\/nologin(\/)?\$/ && $7!~/(\/usr)?\/bin\/false(\/)?\$/) {
print $1 " " $6 }' /etc/passwd | while read -r user dir; do
  if [ -d "$dir" ]; then
    file="$dir/.forward"
    if [ ! -h "$file" ] && [ -f "$file" ]; then
      echo "User: \"$user\" file: \"$file\" exists"
    fi
  fi
done

Expected Result

No output should be returned.

Remediation

Command Line

Making global modifications to users' files without alerting the user community can result in unexpected outages and unhappy users. Therefore, it is recommended that a monitoring policy be established to report user .forward files and determine the action to be taken in accordance with site policy.

The following script will remove .forward files from interactive users' home directories:

#!/bin/bash
awk -F: '($1!~/(root|halt|sync|shutdown)/ &&
$7!~/^(\/usr)?\/sbin\/nologin(\/)?\$/ && $7!~/(\/usr)?\/bin\/false(\/)?\$/) {
print $6 }' /etc/passwd | while read -r dir; do
  if [ -d "$dir" ]; then
    file="$dir/.forward"
    [ ! -h "$file" ] && [ -f "$file" ] && rm -r "$file"
  fi
done

Default Value

N/A

References

N/A

CIS Controls