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.