Eric Byres, Chief Technology Officer,Byres Security Inc.

Tofino OPC Enforcer Technology

Securing OPC Classic Control Systems

Why is OPC Classic So Hard to Secure?

• OPC Classic is the world’s leading technology for integrating different automation products.

• Formerly known as OLE for Process Control, (where OLE stood for Object Linking and Embedding)

• Includes all OPC standards that are based on Microsoft's DCOM Technology (i.e. all but OPC-UA)

• Unfortunately OPC is famous for its poor security…

OPC Classic

• Most protocols use Fixed Port Numbers to identify the application to handle an incoming packet

• Similar to an extension for “accounts payable” on a company phone system

• Example: Most Modbus TCP slaves use port 502

Typical TCP/IP Protocols

Modbus Slave PLC

Modbus MasterOperator Station

Modbus Command (Dst Port = 502)

Modbus Reply (Src Port = 502)

• OPC Classic dynamically assigns TCP ports to each executable process serving objects on a server

• Clients discover port associated with an object by connecting to the server and sending messages like:

“find COM object XXX for me and tell me what port it is on“

OPC Classic (aka OPC DCOM)

OPC ServerOPC Connection Request (Port 135)

OPC DA Connection (Port 12345)

Server Response: Use Port 12345

OPC DA Data (Port 12345)

OPC Client

2222 Rockwell-CSP

• Because OPC is free to use any port between 1024 and 65535 it is “IT firewall unfriendly”• You don’t know in advance what port the server will use

• So you can’t define the firewall rule

• You have to leave all ports open on your firewall

• Configuring your firewall to leave such a wide range of ports open creates a serious security hole

Until Now - An “Unfirewallable” Protocol

2404 IEC 60870-5-104 5000 Mitsibishi MELSCQNA5450 PI Data Historian9100 Omron FINSAnd 1000’s more!

• DCOM callbacks in OPC are not handled on the same connection that is used for client/server calls

• Some OPC servers reject the first few connection attempts after they tell the client to use a specific port, completely breaking most firewall state engines!

• All this has made the industry consider OPC Firewalls virtually impossible

It Gets Worse! OPC/DCOM in the Real World

The Tofino OPC Classic Enforcer

• Loadable security module that makes the Tofino Firewall “OPC-aware”

• Uses deep packet inspection technology to manage OPC traffic behind the scenes

What is the Tofino OPC Classic Enforcer?

• Enforcer intercepts connection requests from the OPC client and checks:• Is it to an approved server?

• Is it from client approved to talk to that server?

• Is it a properly formed OPC connection request message?

How OPC Enforcer Works

OPC Server

OPC Client

OPC Conn Req

Invalid Request

OPC Conn Req

• Next Enforcer intercepts connection reply from the OPC server and checks:• Is it a properly formed OPC connection reply message?

• Is it to the client that made the request?

• What TCP port is the server telling the client to use?

How OPC Enforcer Works

OPC Server

OPC Client

OPC Conn ReplyOPC Conn Reply

It’s a good reply and Server wants Client to

use TCP port 5555

• Enforcer momentarily opens the TCP port it found in the message, with the following restrictions:• Only for communications between that client and server

• Only if the client uses the specified port

• Only if proper TCP session occurs within X seconds

How OPC Enforcer Works

OPC Server

OPC Client

OPC Data Req

Invalid Client/Port

Data Req (5555)

OPC DataOPC Data

• Is not from approved clients and servers

• Tries to use other TCP port numbers

• Tries to “borrow” port numbers from other clients or servers

• Is not well formed RPC connection requests

OPC Enforcer Blocks Dangerous Traffic

OPC Server

OPC Client

Invalid Port #

OPC DataOPC Data

Invalid ClientInvalid Server

Malformed Msg

• First-ever application of connection tracking technology to industrial protocols

• Automatically tracks TCP ports assigned by OPC servers for data connections

• Dynamically opens tracked ports in firewall only when they are needed

• Tofino ‘Sanity Check’ blocks any OPC requests not conforming to the DCE/RPC standard

• Supports multiple OPC clients and servers

Why Tofino OPC Enforcer is Unique

• Manage all traffic on systems that use OPC DA, HDA or A&E

• Secure data transfers to and from data historians and supervisory applications

• Protect safety instrumentation systems• Combine with Tofino VPN LSM for ultra secure

remote OPC connections

Typical Applications

• Simple to use – no changes needed to any OPC servers or clients

• Just install on the network and configure which servers and clients you want to communicate

• Works with OPC DA, HDA and A&E standards• Secures against both accidental and malicious traffic• Endorsed by the OPC Foundation

Benefits of Tofino OPC Enforcer

• Tofino OPC Enforcer LSM• Available Now

• Requirements:• Tofino Security Appliance

• Tofino Central Management Platform version 1.6 or better

• Tofino Firewall LSM

• Additional Resources:• www.tofinosecurity.com/opc

• OPC Foundation Endorsed White Paper, “Securing Your OPC Classic Control System”

Ordering the Tofino OPC Enforcer