docs: add Module 04 references to main README and Module 03 Next Steps

Author: wcoleman-rti

README.md

@@ -13,6 +13,7 @@ This repository contains documentation and module demo applications showcasing d
   - [Module 01: Digital Operating Room](#module-01--digital-operating-room)
   - [Module 02: RTI Recording Service & RTI Replay Service](#module-02--rti-recording-service--rti-replay-service)
   - [Module 03: Remote Teleoperation with RTI Real-Time WAN Transport](#module-03--remote-teleoperation-with-rti-real-time-wan-transport)
+  - [Module 04: Security Threat Demonstration](#module-04--security-threat-demonstration)
 - [Hands-On: Architecture](#hands-on-architecture)
 - [Architecture Overview](#architecture-overview)
   - [Data Types](#data-types)
@@ -73,6 +74,8 @@ The RTI MedTech Reference Architecture demonstrates use cases and capabilities o
 
 - ### [Module 03](./modules/03-remote-teleoperation/) : Remote Teleoperation with RTI Real-Time WAN Transport
 
+- ### [Module 04](./modules/04-security-threat/) : Security Threat Demonstration
+
 ## Hands-On: Architecture
 
 RTI System Designer allows you to graphically design, configure, examine, and share Connext system architectures.
@@ -269,4 +272,5 @@ Check out the the [system_arch](./system_arch/) folder, where the system archite
 - [Connext Real-Time WAN Transport](https://community.rti.com/static/documentation/connext-dds/7.3.0/doc/manuals/connext_dds_professional/users_manual/users_manual/PartRealtimeWAN.htm) *, used in Module 03: Remote Teleoperation with RTI Real-Time WAN Transport*
 - [RTI Routing Service](https://community.rti.com/static/documentation/connext-dds/7.3.0/doc/manuals/connext_dds_professional/services/routing_service/index.html) *, used in Module 03: Remote Teleoperation with RTI Real-Time WAN Transport*
 - [RTI Cloud Discovery Service](https://community.rti.com/static/documentation/connext-dds/7.3.0/doc/manuals/addon_products/cloud_discovery_service/index.html) *, used in Module 03: Remote Teleoperation with RTI Real-Time WAN Transport*
+- [RTI Security Plugins Users Manual](https://community.rti.com/static/documentation/connext-dds/7.3.0/doc/manuals/connext_dds_secure/users_manual/index.html) *, used in Module 04: Security Threat Demonstration*
 - [RTI Connext Third-Party Software](https://community.rti.com/static/documentation/connext-dds/7.3.0/doc/manuals/connext_dds_professional/release_notes_3rdparty/index.html)

modules/03-remote-teleoperation/README.md

@@ -97,4 +97,6 @@ Test how the system handles network interruptions.
 
 ## Next Steps
 
+Check out [Module 04: Security Threat Demonstration](../04-security-threat/), which demonstrates what happens when a malicious application attempts to tamper with surgical arm commands or steal patient vital signs — and how DDS Security blocks these attacks.
+
 Head back to the [main README](../../README.md) and pick up with the [Hands-On: Architecture](../../README.md#hands-on-architecture) section to learn more about the system architecture.