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ATT&CK Technique

Install Root Certificate

T1553.004 · defense-impairment

Adversaries may install a root certificate on a compromised system to avoid warnings when connecting to adversary controlled web servers. Root certificates are used in public key cryptography to identify a root certificate authority (CA). When a root certificate is installed, the system or application will trust certificates in the root's chain of trust that have been signed by the root certificate.

Certificates are commonly used for establishing secure TLS/SSL communications within a web browser. When a user attempts to browse a website that presents a certificate that is not trusted an error message will be displayed to warn the user of the security risk. Depending on the security settings, the browser may not allow the user to establish a connection to the website.

Installation of a root certificate on a compromised system would give an adversary a way to degrade the security of that system. Adversaries have used this technique to avoid security warnings prompting users when compromised systems connect over HTTPS to adversary controlled web servers that spoof legitimate websites in order to collect login credentials. Atypical root certificates have also been pre-installed on systems by the manufacturer or in the software supply chain and were used in conjunction with malware/adware to provide Adversary-in-the-Middle capability for intercepting information transmitted over secure TLS/SSL communications.

Root certificates (and their associated chains) can also be cloned and reinstalled. Cloned certificate chains will carry many of the same metadata characteristics of the source and can be used to sign malicious code that may then bypass signature validation tools (ex: Sysinternals, antivirus, etc.) used to block execution and/or uncover artifacts of Persistence. In macOS, the Ay MaMi malware uses /usr/bin/security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain /path/to/malicious/cert to install a malicious certificate as a trusted root certificate into the system keychain.

LinuxmacOSWindows
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Actors Using This

1
china_state_sponsored_mandiant_unc4841_barracuda_esg_zero_day_specialistUNC4841
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Atomic Tests

7
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
shelevatedlinuxInstall root CA on CentOS/RHEL
Creates a root CA with openssl 
openssl genrsa -out #{key_filename} 4096
openssl req -x509 -new -nodes -key #{key_filename} -sha256 -days 365 -subj "/C=US/ST=Denial/L=Springfield/O=Dis/CN=www.example.com" -out #{cert_filename}
cp #{cert_filename} /etc/pki/ca-trust/source/anchors/
update-ca-trust
shelevatedlinuxInstall root CA on FreeBSD
Creates a root CA with openssl 
openssl genrsa -out #{key_filename} 4096
openssl req -x509 -new -nodes -key #{key_filename} -sha256 -days 365 -subj "/C=US/ST=Denial/L=Springfield/O=Dis/CN=www.example.com" -out #{cert_filename}
cp #{cert_filename} /usr/local/share/certs/
certctl rehash
shelevatedlinuxInstall root CA on Debian/Ubuntu
Creates a root CA with openssl 
mv #{cert_filename} /usr/local/share/ca-certificates
sudo update-ca-certificates
shelevatedmacosInstall root CA on macOS
Creates a root CA with openssl 
sudo security add-trusted-cert -d -r trustRoot -k "/Library/Keychains/System.keychain" "#{cert_filename}"
powershellelevatedwindowsInstall root CA on Windows
Creates a root CA with Powershell 
$cert = Import-Certificate -FilePath #{pfx_path} -CertStoreLocation Cert:\LocalMachine\My
Move-Item -Path $cert.PSPath -Destination "Cert:\LocalMachine\Root"
powershellelevatedwindowsInstall root CA on Windows with certutil
Creates a root CA with certutil 
certutil -addstore my #{pfx_path}
powershellelevatedwindowsAdd Root Certificate to CurrentUser Certificate Store
The following Atomic test simulates adding a generic non-malicious certificate to the CurrentUser certificate store. This behavior generates a registry modification that adds the cloned root CA certificate in the keys outlined in the blog. Keys will look like - \SystemCertificates\CA\Certificates or \SystemCertificates\Root\Certificates Reference: https://posts.specterops.io/code-signing-certificate-cloning-attacks-and-defenses-6f98657fc6ec 
IEX (IWR 'https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1553.004/src/RemoteCertTrust.ps1' -UseBasicParsing)
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Mitigations

2
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1028Operating System Configuration

Operating System Configuration involves adjusting system settings and hardening the default configurations of an operating system (OS) to mitigate adversary exploitation and prevent abuse of system functionality. Proper OS configurations address security vulnerabilities, limit attack surfaces, and ensure robust defense against a wide range of techniques.

Disable Unused Features
  • Turn off SMBv1, LLMNR, and NetBIOS where not needed.
  • Disable remote registry and unnecessary services.
Enforce OS-level Protections
  • Enable Data Execution Prevention (DEP), Address Space Layout Randomization (ASLR), and Control Flow Guard (CFG) on Windows.
  • Use AppArmor or SELinux on Linux for mandatory access controls.
Secure Access Settings
  • Enable User Account Control (UAC) for Windows.
  • Restrict root/sudo access on Linux/macOS and enforce strong permissions using sudoers files.
File System Hardening
  • Implement least-privilege access for critical files and system directories.
  • Audit permissions regularly using tools like icacls (Windows) or getfacl/chmod (Linux/macOS).
Secure Remote Access
  • Restrict RDP, SSH, and VNC to authorized IPs using firewall rules.
  • Enable NLA for RDP and enforce strong password/lockout policies.
Harden Boot Configurations
  • Enable Secure Boot and enforce UEFI/BIOS password protection.
  • Use BitLocker or LUKS to encrypt boot drives.
Regular Audits
  • Periodically audit OS configurations using tools like CIS Benchmarks or SCAP tools.
Tools for Implementation Windows
  • Microsoft Group Policy Objects (GPO): Centrally enforce OS security settings.
  • Windows Defender Exploit Guard: Built-in OS protection against exploits.
  • CIS-CAT Pro: Audit Windows security configurations based on CIS Benchmarks.
Linux/macOS
  • AppArmor/SELinux: Enforce mandatory access controls.
  • Lynis: Perform comprehensive security audits.
  • SCAP Security Guide: Automate configuration hardening using Security Content Automation Protocol.
Cross-Platform
  • Ansible or Chef/Puppet: Automate configuration hardening at scale.
  • OpenSCAP: Perform compliance and configuration checks.
M1054Software Configuration

Software configuration refers to making security-focused adjustments to the settings of applications, middleware, databases, or other software to mitigate potential threats. These changes help reduce the attack surface, enforce best practices, and protect sensitive data.

Conduct a Security Review of Application Settings
  • Review the software documentation to identify recommended security configurations.
  • Compare default settings against organizational policies and compliance requirements.
Implement Access Controls and Permissions
  • Restrict access to sensitive features or data within the software.
  • Enforce least privilege principles for all roles and accounts interacting with the software.
Enable Logging and Monitoring
  • Configure detailed logging for key application events such as authentication failures, configuration changes, or unusual activity.
  • Integrate logs with a centralized monitoring solution, such as a SIEM.
Update and Patch Software Regularly
  • Ensure the software is kept up-to-date with the latest security patches to address known vulnerabilities.
  • Use automated patch management tools to streamline the update process.
Disable Unnecessary Features or Services
  • Turn off unused functionality or components that could introduce vulnerabilities, such as debugging interfaces or deprecated APIs.
Test Configuration Changes
  • Perform configuration changes in a staging environment before applying them in production.
  • Conduct regular audits to ensure that settings remain aligned with security policies.
Tools for Implementation Configuration Management Tools
  • Ansible: Automates configuration changes across multiple applications and environments.
  • Chef: Ensures consistent application settings through code-based configuration management.
  • Puppet: Automates software configurations and audits changes for compliance.
Security Benchmarking Tools
  • CIS-CAT: Provides benchmarks and audits for secure software configurations.
  • Aqua Security Trivy: Scans containerized applications for configuration issues.
Vulnerability Management Solutions
  • Nessus: Identifies misconfigurations and suggests corrective actions.
Logging and Monitoring Tools
  • Splunk: Aggregates and analyzes application logs to detect suspicious activity.
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Detection Coverage

2/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) 10
Analytics (MITRE CAR) 1
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) none
Vuln scan (Nuclei) none
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CAR Analytics

1
MITRE Cyber Analytics Repository - field-tested detection logic for this technique, written as pseudocode/queries you adapt to your own SIEM (Splunk, Sentinel, EQL). Each is a ready starting point for a detection rule, not just a description.
CAR-2021-05-001Moderate coverageAttempt To Add Certificate To Untrusted Store

Adversaries may add their own root certificate to the certificate store, to cause the web browser to trust that certificate and not display a security warning when it encounters the previously unseen certificate. This action may be the precursor to malicious activity.

Splunk - Splunk code
| tstats count min(_time) as firstTime values(Processes.process) as process max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name=*certutil* (Processes.process=*-addstore*) by Processes.parent_process Processes.process_name Processes.user
Pseudocode - Pseudocode - detect attempts to add a certificate to a certificate store
processes = search Process:Create
addstore_commands = filter processes where (
  exe =”C:\Windows\System32\certutil.exe” AND command_line="*-addstore*” )
output addstore_commands
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Comply & Defend

NIST 800-53CM-06, CM-07, CM-10, IA-09, SC-20, SI-04
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