The implementation of sensors, together with communication tools, into industrial environments becomes an active field of science and technology, under the name Industrial Internet of Things (IIoT). IIoT faces significant concern because it exposes its systems to increasing cyber-security threats. Literature presents multiple types of threats and defense solutions to combat them. Research on the security aspects of IIoT in intelligent industrial systems will be studied through bibliometric analysis according to this paper. The paper performs a bibliometric study of scientific journal publications, which is classified using time periods together with researchers and essential topics. The paper analyzes the security threats that confront IIoT, while presenting defense methods from the literature along with identifying research deficiencies regarding IIoT-based intelligent industrial system security.