In English: Virus, Viruses. I don't care whether you want to use viruses or virii when you mean a computer virus, but virii definitely ain't English. It ain't even Latin:
Virus, Viri. There ain't no virii in Latin. (virus in nominative singular, virum in accusative singular, viri in genitive singular, viri in nominative plural, viri in accusative plural). And cactuses? No cactii in Latin...: Cactus, Cacti.


Two computer viruses = two virii? OK, fair enough, but not in Latin . Definitely not in Latin