In "Star Trek: The Next Generation" the Borg is a species of cyborg that ruthlessly seeks to incorporate all sentient life into itself; their slogan is "You will be assimilated. Resistance is futile." In hacker parlance, the Borg is usually Microsoft, which is thought to be trying just as ruthlessly to assimilate all computers and the entire Internet to itself (there is a widely circulated image of Bill Gates as a Borg). Being forced to use Windows or NT is often referred to as being "Borged". Interestingly, the Halloween Documents reveal that this jargon is live within Microsoft itself. (Other companies, notably Intel and UUNet, have also occasionally been equated to the Borg.) See also Evil Empire, Internet Exploiter.
In IETF circles, where direct pressure from Microsoft is not a daily reality, the Borg is sometimes Cisco. This usage commemmorates their tendency to pay any price to hire talent away from their competitors. In fact, at the Spring 1997 IETF, a large number of ex-Cisco employees, all former members of Routing Geeks, showed up with t-shirts printed with "Recovering Borg".