IoT Security Guideline for Digital Signage

Release Date: 27 Sep 2024 2479 Views

Contents

1. Introduction

With the rapid development of digital display panel technology, digital signage has become an important Internet of Things (IoT) device for modern businesses to disseminate public information and brand promotions. There are many types of digital signage for wide range of applications, e.g. information displays, electronic billboards, interactive systems, digital advertisement panels, etc.

These highly interconnected display systems, through the Internet of Things (IoT) technology, have achieved remote content management, real-time information updates and interactive functions, greatly enhancing the flexibility and effectiveness of advertising and information dissemination. However, due to their network connectivity, digital signage is also vulnerable to a series of cybersecurity challenges, which might affect the normal operation of signage, and endanger the network and data security connected to them.

To address these challenges, this guideline aims to provide best practices and security measures for digital signage users, operators, advertisers and technology providers, in order to enhance the safety and privacy of the public, also ensure the long-term sustainable development of digital signage technology.

Various types of digital signages (image source: iStockPhoto)

2. Potential Threats

Data Leakage

Sensitive information stored in the digital signage may be accessed by unauthorised third parties, and data in transit (e.g. when updating content) may be intercepted.

Malware Infection

The system of the digital signage may be implanted with viruses, trojans or other malicious programs, which may result in system malfunctions, inappropriate displays, etc. Malware may also be introduced through the USB port or network connection, which may affect the normal operation of the digital signage.

Unauthorised Access

Hackers may remotely control the digital signage system to change the display content or functions. Weak passwords or insecure authentication mechanisms may be easily exploited, resulting in unauthorised operation of the digital signage.

Content Defacement

Information displayed on the digital signage may be tampered with, resulting in the dissemination of incorrect or misleading information on displays in public places and the system may be hijacked for other advertising or promotional purposes.

System Tampering

The hardware, software and configuration settings of the digital signage may be altered or replaced, resulting in display anomalies or security breaches that affect their functionality or security.

3. Architecture of Digital Signage System

A common architecture for signage systems consists of four layers: Application Layer, Management Layer, Network Layer and Device Layer.

Common Architecture of Digital Signage

3.1 Application Layer

The Application Layer includes backend database containing signage data, business compliance information, and content management systems for content protection and data retention. In the guidelines, we will focus on the security of signage data and content compliance.

Multiple applications on application layer user interface (Image Source: digitalsignage.com)

By accessing the application server, operators can deploy or adjust the content information displayed on signage devices for optimal presentation.

3.2 Management Layer

The Management Layer, usually through the on-premises server or cloud server, involves device management (firmware, configuration, system updates), event and data monitoring, and maintenance. The guidelines focus on the security of the management system and user operations.

Management layer for multiple digital signage devices user interface (Image Source: digitalsignage.com)

By accessing the management server, administrators can manage one or more signage devices to perform device management and event monitoring.

3.3 Network Layer

This includes the transport payload of the signage using various communication technologies and protocols, such as Wi-Fi, LAN, and 4G/5G, along with security measures like firewalls and intrusion detection. These technologies must ensure stable and reliable data transmission in various environments.

Digital signage are connected and managed by wireless protocols such as Wi-Fi through network settings in its underlying operating system (Image Source: androidguys)

3.4 Device Layer

The Device Layer is the starting point of digital signage, including the physical devices of the signage and the included physical interfaces, etc.

Users can interact through user interface of the digital signage (Image source: iStockPhoto)

4. Security Best Practice

Categorizing the digital signage system into application, management, network, and device layers helps in comprehensively understanding and managing potential security risks. This layered approach allows for targeted security measures to be implemented at each level, addressing specific threats and challenges, thereby enhancing overall security and system reliability.

4.1 Application Layer

A. Data Privacy Security
Data Protection	Implement encryption for all sensitive data during storage and transmission. Enforce strict data access control and user authentication mechanisms (e.g. strong password and multi-factor authentication) within the system to limit who can view or manipulate content. Schedule regular data backups and securely store the backup data. Develop a comprehensive data breach incident response plan and procedure to swiftly address and mitigate the impact of data leaks.
B. Standards and Compliance
Data Custody	Ensure compliance with all relevant data protection and privacy laws and regulations to maintain legal and ethical standards. Conduct regular compliance audits to verify adherence to data protection and privacy regulations. Keep necessary records for compliance audit purpose.
C. Content Management
Content Protection	Establish a content publication review process to verify the legality and compliance of all published content. Define a content publication policy to govern the review process on content addition, modification, removal, scheduling and verification before taking effective. Securely reinforce the content management system with additional safeguards to prevent unauthorised content modifications. Monitor the integrity of the content distribution process to detect and prevent content tampering. Define and implement content backup policy to ensure the content can be recovered in a timely manner after data is lost or tampered with.
Data Retention	Regularly remove old or unnecessary data to reduce the storage of potentially sensitive or outdated information.

4.2 Management Layer

A. Device Management
Device Security	Change default credentials on all devices to strong, unique credentials. Regularly update devices with the latest firmware to address security vulnerabilities. Equip devices with fail-safe modes that automatically recover to a normal state in response to system crash or application issues. Disable unused services or features to reduce attack surfaces.
System Security	Keep the system updated with the latest patches to mitigate known security vulnerabilities. Install antivirus software and ensure its definition library is kept up to date to protect against malware. Restrict permissions on the system to prevent the execution of malicious software. Monitor abnormal network traffic to identify and respond to potential malicious activities.
Account Security	Establish a robust password policy that requires regular password changes to strengthen account security. Ensure all remote access is encrypted and authenticated to prevent unauthorised access to the system. Log and monitor all user access to the system. Implement network isolation measures to limit access to critical systems.
B. Data and Log Event Monitoring
Incident Response and Handling	Define clear security incident response processes and assign responsibilities to ensure a coordinated response to incidents. Users may refer to the “Incident Response Guideline for SMEs”. Conduct regular security drills to evaluate and improve the effectiveness of incident response plans.
Monitoring and Log Management	Implement a centralized log management system to monitor and analyse security logs for early detection of threats. Develop a logging retention policy that complies with legal and audit requirements for record-keeping.
Risk Assessment and Mitigation	Perform regular risk assessments to proactively identify and address new threats and vulnerabilities. Create risk mitigation plans and execution strategies to manage identified risks effectively.

4.3 Network Layer

A. Network Security
Network Security	Deploy firewalls and intrusion-detection systems to protect against external threats. Conduct regular network security audits and vulnerability scans to identify and rectify potential security weaknesses. Disable unnecessary network services, such as SNMP, telnet, etc. if not in use.
B. Wireless Security
Wireless Security	Use the latest encryption Wi-Fi protocol, at least WPA2-PSK (Pre-shared Key) with AES protocol or above. Use dedicated Wi-Fi network and avoid using public Wi-Fi for device management.

4.4 Device Layer

A. Physical Security
Physical Security	Restrict physical access to the devices, such as checking all locks securely, ensuring only authorised personnel can perform maintenance and inspections to the system mother board.
B. External Interface Port Access Control
External Interface Port Access Control	Restrict physical access to external interface ports e.g. USB, HDMI, network ports, etc. Disable ports when not in use. Monitor log events of unexpected usage of ports. Disable Auto-Run and Auto-Play to prevent automatic execution of potentially malicious files from USB device.
C. Initial Configuration
Initial Configuration	Prioritize the modification of default settings when deploying new signage systems or devices, such as initial passwords, reconfigure network information and other critical parameters.

5. Conclusion and Recommendation

Given the sophisticated systems of the digital signage itself, also the connection between signage and organisation’s internal system, it also creates entry points for potential cyber threats.

HKCERT recommends that users and business owners adopt a holistic approach to mitigate the associated security risks in each layer of digital signage ecosystem.

In addition to the above, attention should be given to the training of operators of digital signage. Safety awareness training should be provided to all users with reference to clear safety and security usage contingency guidelines and best practices to enhance users' understanding of safety best practices.

Furthermore, it's crucial to emphasize vendor management by selecting vendors that prioritize security in their products and services. Regularly review the security policies of third-party vendors interacting with digital signage systems to ensure comprehensive protection.

6. Reference

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