Does the 4G cellular router support VPN encrypted transmission? A Deep Dive into the "Invisible Shield" of Industrial Network Security
In the era of Industry 4.0, factory equipment, sensors, and control systems are connected to the internet via 4G cellular routers, enabling intelligent scenarios such as remote monitoring and predictive maintenance. However, the increased network openness has also brought about security risks: in 2023, global industrial control system (ICS) attack incidents increased by 67% year-on-year, with 43% of attacks initiated through unencrypted communication links. As the "bridge" connecting field devices to cloud platforms, the VPN encrypted transmission capability of 4G cellular routers has become a core technology for ensuring data security. This article systematically analyzes the value and implementation path of VPN encrypted transmission for 4G cellular routers from four dimensions: technical principles, application scenarios, implementation methods, and future trends.
Industrial network transmission data contains three types of sensitive information:
Device control commands: such as PLC start/stop and valve opening adjustments, which, if tampered with, could lead to equipment damage or production accidents;
Process parameters: such as chemical reaction temperatures and semiconductor wafer etching times, whose leakage could pose intellectual property risks;
Personnel location data: such as mine personnel trajectories and power inspection routes, whose misuse could endanger personal safety.
Case Study: In 2021, an automobile manufacturing plant was attacked due to unencrypted Modbus TCP communication. Hackers altered welding robot parameters, resulting in welding defects in an entire batch of car bodies and direct losses exceeding $2 million.
Man-in-the-Middle (MITM) Attacks: Hackers intercept and tamper with transmitted data through ARP spoofing or DNS hijacking;
Data Leakage: Unencrypted process parameters may be stolen by competitors;
Device Hijacking: Unencrypted OPC UA protocols may be exploited to remotely control industrial robots.
Experimental Data: In an unencrypted industrial Ethernet network, over 90% of Modbus TCP command content can be parsed within 5 minutes using the Wireshark packet capture tool.
VPN (Virtual Private Network) constructs a virtual private network through tunneling technology, encryption algorithms, and identity authentication, providing end-to-end security for industrial data transmission. Its core value is reflected in three major aspects:
VPN encapsulates original data within an encrypted tunnel, making it unreadable even if intercepted by hackers. Mainstream encryption algorithms include:
Symmetric Encryption: AES-256 (256-bit key length), which offers fast encryption/decryption speeds and is suitable for high real-time scenarios;
Asymmetric Encryption: RSA-2048 (2048-bit key length), used for key exchange and offering higher security;
National Cryptographic Algorithms: SM4 (symmetric) and SM2 (asymmetric), which meet the requirements of China's Cybersecurity Classification Protection 2.0 for domestic cryptographic algorithms.
Performance Comparison:
| Algorithm Type | Encryption Speed | Security Level | Industrial Scenario Suitability |
| AES-256 | Fast | High | PLC control commands, video stream transmission |
| RSA-2048 | Slow | Extremely High | Initial key exchange, remote authentication |
| SM4 | Fast | High | Domestic equipment-intensive fields such as energy and transportation |
VPN prevents unauthorized device access through the following mechanisms:
Pre-Shared Key (PSK): Suitable for scenarios with a small number of devices, requiring manual key configuration;
Digital Certificates: Based on the PKI system, issuing unique certificates for each device and supporting revocation and updates;
Dynamic Tokens: Generating one-time passwords by combining time and device ID to resist replay attacks.
Case Study: A smart grid project adopted the digital certificate authentication function of the USR-G809 4G cellular router, issuing X.509 certificates for each smart meter and completely eliminating the risk of counterfeit device access.
VPN can implement fine-grained permission management in conjunction with Access Control Lists (ACLs):
IP-based Filtering: Only allowing devices from specific IP segments to access PLCs;
Port-based Filtering: Only opening necessary ports such as Modbus TCP (port 502);
Protocol-based Filtering: Prohibiting HTTP plaintext protocols and enforcing HTTPS or MQTT over TLS.
| # ACL rule configuration snippet for the USR-G809 router |
| access-list 101 permit tcp host 192.168.1.100 host 10.0.0.1 eq 502 |
| access-list 101 deny tcp any any eq 502 |
IPSec (Internet Protocol Security) is the most widely used VPN protocol in the industrial sector, with core features including:
Dual Encryption: AH (Authentication Header) provides data integrity verification, while ESP (Encapsulating Security Payload) provides encryption and authentication;
NAT Traversal: Supporting NAT-T (NAT Traversal) to adapt to private network environments;
High Compatibility: Seamless interoperability with devices from Huawei, Cisco, and other vendors.
Typical Scenarios:
PLC data synchronization across factories;
Remote maintenance of energy enterprise headquarters and wind farms.
Configuration Key Points:
Select IKEv2 (more secure than IKEv1) as the key exchange protocol;
Enable PFS (Perfect Forward Secrecy) to prevent historical data decryption in case of private key leakage.
OpenVPN, based on SSL/TLS, can be deployed on industrial equipment including:
Dynamic IP Adaptation: Adapting to mobile device access through certificate + username/password dual-factor authentication;
Low Bandwidth Consumption: Using the LZ4 compression algorithm to reduce transmission delays in weak network environments at industrial sites.
Case Study:
An agricultural IoT project used the OpenVPN function of the USR-G809 to encrypt and transmit field sensor data to the cloud. Even under 2G networks, the data packet loss rate remained below 0.5%.
WireGuard is renowned for its simplicity, efficiency, and security, with core design features including:
Only 4,000 lines of code (compared to approximately 600,000 lines for IPSec), resulting in fewer vulnerabilities;
Using the Noise protocol framework to resist quantum computing attacks;
Kernel-level implementation: Directly handling encryption in the Linux kernel, reducing latency by over 50%.
Industrial Adaptability:
Suitable for RTOS (Real-Time Operating System) devices;
Supporting ARM Cortex-M series low-power chips.
Experimental Data:
At 100Mbps bandwidth, WireGuard's throughput is 30% higher than IPSec, with a 20ms lower latency.
| # IPSec configuration example for the USR-G809 |
| crypto isakmp policy 10 |
| encryption aes 256 |
| authentication pre-share |
| group 5 |
| crypto ipsec transform-set MY_SET esp-aes 256 esp-sha-hmac |
Hardware Acceleration: Choose a router CPU that supports the AES-NI instruction set (such as the Cortex-A55 core in the USR-G809);
MTU Adjustment: Set the VPN tunnel's MTU to 1400 bytes to avoid IP fragmentation;
Multi-threaded Encryption: Enable the router's multi-core encryption engine to improve AES-256 processing speed.
Recommended Testing Tools:
iperf3: Measure the actual bandwidth of the VPN tunnel;
Wireshark: Verify whether data is encrypted (ESP protocol packets should be displayed).
Traditional VPNs are based on "network boundary defense," while zero trust advocates for "default distrust, always verify." 4G cellular routers will integrate:
Continuous Identity Verification: Dynamically adjusting permissions through device behavior analysis (such as traffic patterns and access times);
Micro-segmentation: Dividing industrial networks into multiple security domains to limit the lateral movement of VPN tunnels.
AI can analyze abnormal patterns in VPN traffic, such as:
DDoS Attack Detection: Identifying abnormally high VPN connection requests;
Data Leakage Alerts: Detecting the exfiltration of sensitive information hidden within encrypted tunnels.
Case Study:
A petrochemical enterprise deployed an AI-based VPN monitoring system, successfully intercepting an attack that attempted to steal process parameters through an IPSec tunnel. The attack traffic was blocked within just 87 seconds.
