A historical reference is a product, tool, or vendor mentioned for context even though it is no longer operating or actively supported. In cyber security writing, these references help explain how a market, tactic, or control has evolved without implying the product is a current option.
This matters because security decisions depend on up-to-date support, patching, and compatibility. A discontinued product may no longer receive fixes, which can turn it into a risk if it remains in use. In real defensive work, historical references are used to compare old and new tools, track how controls developed, or identify legacy systems that still need migration. In attacks, outdated or abandoned software can also be attractive to attackers because it may expose unpatched weaknesses or outdated dependencies. Always treat a historical reference as background information, not as an active security capability.