Avast! (styled avast!) is - both freeware and payable - an antivirus computer program with user interface that includes 41 languages, available to microsoft windows, mac os x and linux users. the name avast is an acronym of "anti-virus – advanced set". the official, and current logo of avast! is a white orb with the letter 'a' on it and an orange circle around it, sticking out to four directions. its developer, avast software a.s. (formerly known as alwil software a.s.