Avast! Free Antivirus is the freeware version of Avast! antivirus software available to Microsoft Windows and Linux users, while Avast! Pro Antivirus is offered to businesses and users that want additional features. Priority updates are delivered automatically using PUSH update technology in Avast! Pro Antivirus. Avast! Pro Antivirus also has a command line scanner and a script blocker.

Avast is a multiple recipient of the Virus Bulletin VB100 Award, for detection of 100% of "in-the-wild" viruses, and is a past winner of the Secure Computing Readers' Trust Award. The name Avast comes from "Anti-Virus-Advanced-Set". Avast! Antivirus is a widely used antivirus program, with 100 million users worldwide as of December 2009.

Avast Free Antivirus Features

• Avast! Antivirus is a widely used antivirus program, with 100 million users worldwide as of December 2009.
• Resident protection comprising individual modules or "shields", each of which can be individually configured or disabled.
• Anti-spyware capabilities
• Anti-rootkit capabilities
• Self-Protection - Prevents malware from terminating avast! processes and damaging avast! files.
• Automatic incremental updates - Updates of both the program and the virus database which is used to identify potential threats - Avast! updates its virus definitions on a regular basis (sometimes multiple updates daily) and this process is automated by default.
• Audible alarms - Vocal warnings and notices such as "Caution, a virus has been detected!" and "Virus database has been updated."
• Boot-time scan (32 bit only) - Users can schedule a boot-time scan to remove infections that load during Windows startup.
• Virus Chest - Quarantine; folder where infected files can be stored. The virus chest also stores vital system files to protect them from damage by malware. Users can also add their own files to the virus chest. Once in the chest, a file cannot be executed; double-clicking the file will instead display information about the file.