Plug leaks in the firewall to improve Ethernet security

Ethernet offers the advantages of high bandwidth communications, a standard interconnection approach, the ability to transmit data easily between multiple communication levels across many control systems and the support of all major suppliers.


Ethernet offers the advantages of high bandwidth communications, a standard interconnection approach, the ability to transmit data easily between multiple communication levels across many control systems and the support of all major suppliers.

This open and widely-ranging connectivity, however, leaves the control system vulnerable to unauthorized access or system disruption, necessitating security precautions. Today’s major threats come from “malware” %%MDASSML%% viruses, worms and Trojans, released from the Internet through the plant network to control systems; unintentional disruption by OEM suppliers/business partners/unauthorized company personnel; and malicious attacks by disgruntled employees.

There is no “one-size-fits-all” security solution. Each company must customize security for its own particular situation. However, manufacturers can start by putting these best practices into operation.

A security plan must balance the access needs of system users with the needs to block access to all others. Representatives from the affected departments must work together to develop policies that define which people are allowed access to which systems for what purposes.

Management must back these policies fully. Poorly planned or unsupported security measures may disrupt normal or emergency system access, be ignored, bypassed or rolled back due to complaints, resulting in a return to the unprotected status quo.

A single firewall that isolates the Internet from the plant network is insufficient protection for the underlying control systems. Once that firewall is breached, or bypassed by internal personnel, the control systems are totally open to access and disruption. Those planning the security system must consider multiple layers of protection between manufacturing departments, independent manufacturing lines and the enterprise system network.

Enforce security policies

Enforcing policies that deal with common security holes can be “low-hanging fruit” when it comes to improving the integrity of your control and enterprise networks. Common security holes need to be “plugged.”

  • • Create new passwords %%MDASSML%% Many people do not change the factory default passwords in industrial Ethernet managed switches and control devices. Unauthorized personnel can easily find the passwords by pulling the user’s manuals off the Web. Others leave passwords on sticky notes attached to screens. Choose a secure, difficult-to-guess password. For example, think of memorable phrases or songs. Use the starting letters of each word and add a number. Change passwords frequently

  • • Don’t invite outside sources to your network %%MDASSML%% Particularly, nasty Internet sites, left behind CDs or USB thumb drives can carry state-of-the-art viruses and zombie code that can open up back door paths that allow outsider control of your systems. A few precautions can prevent malicious code from bypassing your company’s security systems. For example, don’t download Internet material onto thumb drives or CDs, then load them into your business or control system PCs without scanning for viruses. Don’t pick up music CDs or thumb drives from unknown sources. Make sure you scan the laptops of visiting vendors/suppliers.

    • Many companies’ firewalls are improperly configured or use default settings, allowing most traffic to freely flow through. Emerging industrial firewalls allow a broader “defense-in-depth” solution, but most require IT assistance to configure properly. Industrial managed switches typically offer good security functions to start with, that can be managed by plant personnel.

      These security functions include:

      • • Port security %%MDASSML%% Each switch checks the MAC or IP addresses of the plugged-in devices/maintenance laptops with an approved list of such addresses. Unapproved devices are not allowed to communicate

      • • Virtual LANs %%MDASSML%% VLAN settings allow traffic from a group to devices across one or more switches to be isolated from other VLAN groups. Someone accessing one VLAN cannot connect to devices in another VLAN without specific programming in the switch or a router. For complex and large applications, IT assistance will probably be necessary to properly configure VLANs

      • • Physical security %%MDASSML%% Lock existing cables and plug unused port connections with special plastic locking guards. These guards can also provide basic access control to unmanaged switches.

        • <table ID = 'id3002838-0-table' CELLSPACING = '0' CELLPADDING = '2' WIDTH = '100%' BORDER = '0'><tbody ID = 'id3001652-0-tbody'><tr ID = 'id3002671-0-tr'><td ID = 'id3002154-0-td' CLASS = 'table' STYLE = 'background-color: #EEEEEE'> Author Information </td></tr><tr ID = 'id3001982-3-tr'><td ID = 'id3001984-3-td' CLASS = 'table'> Larry Komarek is the product manager, automation, for the Americas Business Unit of Phoenix Contact in Harrisburg, PA. He has more than 30 years experience in automation product marketing and product development involving PLCs, fieldbus and Ethernet networking, machine vision, barcoding and RFID. Komarek holds a bachelor’s degree in industrial management with a minor in computer design from Purdue University. </td></tr></tbody></table>

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