Authentication Issues between entities during protocol message exchange in SCADA Systems

Authentication Issues between entities during protocol

message exchange in SCADA Systems

Manuel Humberto Santander Peláez [email protected]

Agenda

• Introduction

• SCADA protocols

• Authentication Risks

• Remediation

SCADA

• Supervisory Control and Data Acquisition

• Platform used to monitor and control all the variables of a real-time process

• Several variables to monitor

– Pressure inside a water tube used for distribution

– Flow speed of oil

– Amount of electric charge passing inside an electricity transmission line

Components of SCADA platform

Components of SCADA platform (2)

• Remote Terminal Unit (RTU):

– This is a communication device within the SCADA system and is located at the remote substation.

– The RTU gathers data from field devices in memory until the MTU request that information. It also process orders from the SCADA like switch off a transmission line

– It process the commands ordered by the HMI to the field devices


• Data Acquisition System (DAS):

– Gathers information from the MTU

– Generates and store alerts that needs attention from the operator because it can cause impact on the system

• Master Terminal Unit (MTU):

– The MTU is defined as the heart of a SCADA system and is located at the main monitoring center.


• Master Terminal Unit (MTU):

– MTU initiates communication with remote units and interfaces with the DAS and the HMI.

• Human Machine Interface (HMI):

– Interface where the operator logs on to monitor the variables of the system.

– Gathers information from the DAS

– Sends commands to the MTU and wait for response

Electrical process

• Three big steps

– Generation

– Transmission

– Distribution

• Energy is created using any of the following methods

– Thermoelectrical plans

– Nuclear plants

– Hydro electrical plants

Electrical process (2)

• SCADA platform is vital to perform the following when generation takes place:

– Ensure turbines are not having revolutions more than supported

– Generators are not working overloaded

– Energy being generated matches the amount of energy that the transmission line can handle


• Transmission

– Energy being generated needs to be distributed to reach the final users

– 115 KV is the power used to transmit in the wire lines

– Final destination are the substations that handles energy of a specific amount of instalations

– Large number of blocks in a city


• SCADA platform is vital to perform the following when transmission takes place:

– Monitoring of voltage in transmission lines looking for high amount of electricity flowing

– None of them can get overloaded because protections get activated and a blackout appears in all the installations that are controlled by the affected substations


• Distribution

– Energy being generated needs to be distributed to reach the final users

– 115 KV is the power used to transmit in the wire lines

– Final destination are the substations that handles energy of a specific amount of instalations

– Large number of blocks in a city


• SCADA platform is vital to perform the following when distribution takes place:

– Monitoring of voltage in transmission lines looking for high amount of electricity flowing

– Monitoring of voltage in user meters looking for high amount of electricity flowing

Agenda

• Introduction

• SCADA Protocols


• Remediation

SCADA Protocols

• Modbus

• IEC 104

• DNP3

Modbus

Source: Practical Industrial Data Communications

Modbus (2)

• Client/server protocol which operates in a request/response mode

• Three variants:

– Modbus serial RS-232/RS-485: Implemented on serial networks

– Modbus TCP: Used for SCADA platforms where delay is not an issue (Water supply)

– Modbus UDP: Used for SCADA platforms where delay is a big issue (Energy)

Modbus (3)


Modbus (4)

• Modbus protocol structure

– Address field:

• Request frames: Address of the device being targeted by the request

• Response frame: Address of the device responding to request

Modbus (5)


– Function field

• Function requested by the HMI to be performed by the field devices

• In response packets, when the function performed is succeeded, the field device echoes it. If some exception occurred, the most significant bit of the field is set to 1

Modbus (6)

Function NameFunction

Code

Physical Discrete Inputs Read Discrete Inputs 2

Read Coils 1

Write Single Coil 5

Write Multiple Coils 15

Physical Input Registers Read Input Register 4

Read Holding Registers 3

Write Single Register 6

Write Multiple Registers 16

Read/Write Multiple

Registers23

Mask Write Register 22

Read FIFO Queue 24

Read File Record 20

Write File Record 21

Type of access

Data Access

Bit access Internal Bits or Physical

Coils

16-bit

accessInternal Registers or

Physical Output Registers

File Record Access

Modbus (7)

Function NameFunction

Code

Read Exception Status 7

Diagnostic 8

Get Com Event Counter 11

Get Com Event Log 12

Report Slave ID 17

Read Device

Identification43

Encapsulated Interface

Transport43

Type of access

Diagnostics

Other

Modbus (8)


– Data field

• In request paquets, contains the information required to perform the specific function

• In response packets, contains the information requested by the HMI

Modbus (9)


– Error check Field

• CRC-16 on the message frame

• If packet has errors, the field device does not process it

• Timeout is assumed, so the master sends again the packet to attempt again a function execution

IEC 104

• Standard for power system monitoring, control and communications for telecontrol and teleprotection for electric power systems

• Completely compatible with:

– IEC 60870-5-1: Transmission frame formats for standard 60870-5

– IEC 60870-5-5: Basic application functions

IEC 104 (2)

• It has the following features:

– Supports master initiated messages and master/slave initiated messages

– Facility for time sinchronization

– Possibility of classifying data being transmitted into 16 different groups to get the data according to the group

– Cyclic and spontaneous data updating schemes are provided.

IEC 104 (3)


IEC 104 (4)


IEC 104 (5)


IEC 104 (6)

• Link level

Link service

class Function Explanation

S1 SEND / NO REPLY

Transmit message.

No ACK or answer

required

S2 SEND / CONFIRM

Transmit message.

ACK required

S3 REQUEST / RESPOND

Transmit message.

ACK and answer

required

IEC 104 (7)


IEC 104 (8)


• Control field for unbalanced transmissions

IEC 104 (8)


• Control field for balanced transmissions

DNP3

• Set of communication protocols used between components of a SCADA system

• Used for communications between RTU and the IED (field devices)

• Implements the communication levels established by the enhance performance architecture (EPA)

DNP3 (2)

• Enhance performance architecture (EPA)


DNP3 (3)

• Message exchange


DNP3 (4)

• Frame format


DNP3 (5)

• Control Byte


Agenda

• Introduction

• SCADA Protocols


• Remediation

Network technologies in SCADA Systems

• Many SCADA networks still use RS232/RS485 bus to communicate all components

– But also because of the need to access data in a fast way, we also have serial-to-ip gateways to access serial RTU and IED

– Lots of hybrid SCADA networks having serial and IP components

– Vulnerable from outsiders at the corporate network

Lack of authentication in application protocol

• The SCADA protocols does not perform bi-directional authentication to ensure that all parties are trusted

– Only commands are sent

– Data is sent to the IP address configured as master

– All the IP spoofing vulnerabilities works on any MTU or Field device

– Any command can be sent

Lack of confidentiality in application protocol

• The SCADA protocols does not perform any encryption to protect the information – Modbus, IEC 101/104 and DNP3 transmissions

can be checked by any attacker

– Man-in-the-middle can be performed on the network

– MTU traffic can be intercepted and then redirected to any IED with any desired change

– No way to know if traffic is trusted

What could be done?

• Let’s see how a master station puts the current timestamp on an IED

• Let’s see how the attacker changes it

• Can issue writable commands and reading commands

• DEMO TIME!

Agenda

• Introduction

• SCADA Protocols


• Remediation

What you cannot do with SCADA

• Protocol delay is usually a BIG issue in SCADA

– Water supply and Oil SCADA tolerates big delays because it does not have consequences in the process

– Power SCADA is critical. A delay higher than 5 miliseconds could end in a massive blackout because of failure to open a breaker in a substation

– Be careful on what you do to protect your SCADA

SCADA Network Design

Monitor your network

• SCADA traffic baseline is mandatory

– You need to know what applications are doing transit inside your network

– Inside SCADA protocols you monitor applications that gives you information on the industrial process being controlled

– Unauthorized applications could indicate a breach trying to perform operations or gather information on IED

Monitor your network (2)

• Use Network Intrusion Prevention System

– You definitely can use conventional IPS if they are fast enough to avoid delays in your network

– Not all of them support SCADA protocols

– If you have snort, you can write rules for Modbus and DNP3. Otherwise, you need to write your own rules

– Industrial Defender Solution works pretty good as it includes lots of SCADA signatures

• SCADA platforms are designed to last from 10 to 20 years

– Too many technology changes happens in that time

– Lots of security issues to deal with

– Need a solution to avoid any changes inside computers, as intrusions perform changes in filesystem, configurations and system process

Control unauthorized changes to Master Terminal Unit

Control unauthorized changes to Master Terminal Unit (2)

• SCADA platforms are designed to last from 10 to 20 years

– Too many technology changes happens in that time

– Lots of security issues to deal with

– Need a solution to avoid any changes inside computers, as intrusions perform changes in filesystem, configurations and system process

Control unauthorized changes to Master Terminal Unit (3)

• Control any changes inside your SCADA servers

– Mcafee Integrity control works pretty good

– Defines what can be changed by who

– Lots of custom logs to choose from

– Can send events to any SIEM configured in the Network

Monitor attacks to Master Unit

• Host IPS is definitely needed as any attack could change the integrity and stability of a process

• Availability is critical to a SCADA system and cannot be altered

• Conventional Host IPS performs extensive use of CPU and can affect performance inside SCADA

Monitor attacks to Master Unit (2)

• Industrial Defender Host IPS works pretty good

• Works seamless with Siemens Spectrum Platform

• Does not load the machine or needs extensive bandwith to perform its checks

• Central console to perform operations inside the platform

Questions? Comments?

Manuel Humberto Santander Peláez http://manuel.santander.name

http://twitter.com/manuelsantander

[email protected] / [email protected]

Documents

Authentication Issues between entities during protocol message exchange in SCADA Systems