Just as Mac malware -- Mac Defender -- has come to the attention of media and Mac users, Avast Software has released a beta of its new Avast for Mac, a free antivirus program that has entered public beta stage. The app runs three shields, for web, mail and a Mac's file system and features an on-demand scanner with custom scans also available. The Web Shield monitors and filters HTTP traffic and protects against common Javascript-based malware. The File Shield scans application binaries on launch and checks all file modifications, while the Mail Shield monitors and fi
