How do viruses historically copy themselves from one system to another?

While administrative shares can indeed be a method for file sharing and accessing files remotely, viruses historically are more commonly associated with other methods of propagation. The most prevalent ways that viruses have copied themselves from one system to another typically include removable drives, email attachments, and network transfers.

Removable drives were a significant vector in the early days of viruses, as they allowed the transfer of infected files between systems easily, especially before widespread internet connectivity. Email attachments are another common historical method, where users might unknowingly open an infected file sent to them. Network transfers also serve as a prevalent means for viruses to spread within interconnected systems, utilizing shared resources and vulnerabilities in network protocols.

In this context, the option that frequently captures the essence of how viruses have been spread historically encompasses various viable vectors, but the most recognized among these would likely lean towards the use of removable drives or email. While administrative shares could be applicable in some scenarios, it's essential to acknowledge that they are not the primary historical method of virus propagation compared to removable drives, email attachments, and network transfers.