What do you think? Should they become synonyms? If yes, which one should be the main tag?
In computer-security, the word “computer” is redundant at best and misleading at worst. You don't really secure a computer, but a computer system (involving software, policies, network setup and other elements that aren't “computer” per se). The tag should be security.
There are tags in which the word “computer” may be justified, such as computer-networks (as opposed to kinds of graphs) and computer-architecture, and even then I'm unconvinced: shouldn't that be networks and hardware-architecture?