Sequi, a developer of cybersecurity products for industrial control networks, announced the availability of PortBloque S, a serial-to-serial firewall that protects Modbus devices from harmful and unwanted traffic. PortBloque S is the first in a series of planned firewalls aimed at addressing  the inherent vulnerabilities of the Modbus protocol. Advanced deep packet inspection (DPI) technology is used on Modbus traffic to ensure that control systems receive only the commands required for normal operations and not commands that could lead to harmful consequences.PortBloque S enables users to control traffic to the RTU in a granular fashion. Firewall rules can be customized to permit specific Modbus function codes (standard and non-standard), device IDs, registers, and values. Typical applications are filtering inbound radio communications or controlling the data stream on an extended RS-485 link.PortBloque S has two RS232/485/422 ports, one 10/100BaseT Ethernet port, a management port, and supports RTU and ASCII…