In FNET 4.6.3, TCP ISNs are improperly random.
https://www.tenable.com/cyber-exposure/2021-threat-landscape-retrospective
https://www.forescout.com/resources/numberjack-weak-isn-generation-in-embedded-tcpip-stacks/
https://www.cisa.gov/news-events/ics-advisories/icsa-21-042-01