Responsive Navigation
Protect Modbus Devices from Serial Attacks

PortBloque S

("port block")

PortBloque S is a specialized firewall that protects Modbus devices from serial attacks. It provides Modbus RTU/ASCII deep packet inspection (DPI), blocking everything that's harmful or unwanted. The simple web interface makes setup easy. Operators can control Modbus traffic by slave IDs and function codes, and block a command that repeats too soon. Additionally, operators can define a permissible range of slave registers and values to prevent malicious memory access.

• DPI on Modbus RTU/ASCII
• Highly customizable
• 2 DB9 serial (Master, Slave)
• RS-232/422/485 software selectable
• 1 RJ-45 Ethernet (Web)
• Small size approx: 4 x 3 x 1 in
• 0 to 85°C (32 to 185°F)
• Durable metal housing
• Ships with external 5VDC (2A) power supply

Download the Datasheet 
PortBloque S
Serial Firewall with DPI on Modbus RTU/ASCII

$475.00 USD

Made in California

FREE technical support

Protection against Internet attacks

Modbus security that's strictly serial.

Blocks function codes, registers, and values that you have not permitted to specific slave devices.

Blocks a command that repeats too soon to protect slave devices.

Device ID
Function Code
Detailed control of Modbus.

You can select the types of function codes that specific slaves can receive and define accessible read/write ranges for registers and values.

The simple web interface provides detailed control over Modbus traffic. 
Take a look at how easy it is.
Enter the Modbus device IDs of serial slaves you want to protect.
Security - Modbus device IDs
Select the Modbus function codes you want those devices to receive.
Security - Modbus function codes
You can also enter Modbus register and value ranges.
Security - Modbus addresses
And enter the amount of time to wait before a particular Modbus command can be repeated.
Security - Time between Modbus command
You can also enter non-standard Modbus function codes that are in use by your plant. Examples of customer-entered numerical codes and names are shown below.   
Security - custom codes
Direct connect to Modbus slaves. 
Modbus RTU
Modbus ASCII

1 RJ-45 Ethernet
2 DB9 serial (RS-232/422/485 software selectable)
Buy Now

The safe, fast, and secure way to pay online using any major credit card. You don't need a PayPal account.

PortBloque S
$475.00 USD
Typically ships in 5 days via UPS Ground

Can’t purchase right now? Simply use the Order Request form and we’ll send a PayPal invoice to your email.

International Shipping: Please use the Order Request form.

outside the 48 contiguous United States: Please use the Order Request form.

Shipping within the 48 contiguous United States:
 Please select a quantity (up to 5) from the dropdown and click on the 'Buy Now' button. To order a quantity greater than 5, please use the Order Request
PortBloque S (quantity+shipping):