In order to prevent your devices from being used in a DDoS attack through botnets, it is important to take the following steps and follow best practices:

1. Purposeful Security
   Establish purposeful plans and security protocols to secure your network.
2. Maintain Firewalls
   Make sure all firewalls, especially outward-facing ones, are up-to-date and regularly maintained.
3. Keep Records
   Keep logs of security activities and records of machine behavior, such as patching.
4. Frequent Updating and Patching
   Ensure all devices have the latest updates and patches applied.
5. Restrict Device Access
   Restrict access to devices to trusted individuals.
6. Conduct Threat Modeling
   Analyze your system and identify potential attack vectors.
7. Monitor Traffic for Abnormal Behavior
   Utilize both static and dynamic traffic monitoring to detect DDoS attacks early.