Record Events that Modify User/Group Information

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Description

If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d, in order to capture events that modify account changes:

-w /etc/group -p wa -k audit_rules_usergroup_modification
-w /etc/passwd -p wa -k audit_rules_usergroup_modification
-w /etc/gshadow -p wa -k audit_rules_usergroup_modification
-w /etc/shadow -p wa -k audit_rules_usergroup_modification
-w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file, in order to capture events that modify account changes:

-w /etc/group -p wa -k audit_rules_usergroup_modification
-w /etc/passwd -p wa -k audit_rules_usergroup_modification
-w /etc/gshadow -p wa -k audit_rules_usergroup_modification
-w /etc/shadow -p wa -k audit_rules_usergroup_modification
-w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

Rationale

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

Remediation

Shell script

The following script can be run on the host to remediate the issue.

#!/bin/bash

# Perform the remediation
# Perform the remediation for both possible tools: 'auditctl' and 'augenrules'
<ns10:sub idref="xccdf_org.ssgproject.content_value_function_fix_audit_watch_rule" use="legacy"/>
fix_audit_watch_rule "auditctl" "/etc/group" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/group" "wa" "audit_rules_usergroup_modification"
<ns10:sub idref="xccdf_org.ssgproject.content_value_function_fix_audit_watch_rule" use="legacy"/>
fix_audit_watch_rule "auditctl" "/etc/passwd" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/passwd" "wa" "audit_rules_usergroup_modification"
<ns10:sub idref="xccdf_org.ssgproject.content_value_function_fix_audit_watch_rule" use="legacy"/>
fix_audit_watch_rule "auditctl" "/etc/gshadow" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/gshadow" "wa" "audit_rules_usergroup_modification"
<ns10:sub idref="xccdf_org.ssgproject.content_value_function_fix_audit_watch_rule" use="legacy"/>
fix_audit_watch_rule "auditctl" "/etc/shadow" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/shadow" "wa" "audit_rules_usergroup_modification"
<ns10:sub idref="xccdf_org.ssgproject.content_value_function_fix_audit_watch_rule" use="legacy"/>
fix_audit_watch_rule "auditctl" "/etc/security/opasswd" "wa" "audit_rules_usergroup_modification"
fix_audit_watch_rule "augenrules" "/etc/security/opasswd" "wa" "audit_rules_usergroup_modification"

Warning

This rule checks for multiple syscalls related to account changes; it was written with DISA STIG in mind. Other policies should use a separate rule for each syscall that needs to be checked. For example:

  • audit_rules_usergroup_modification_group
  • audit_rules_usergroup_modification_gshadow
  • audit_rules_usergroup_modification_passwd