Avast free Antivirus
The avast! engine also features outstanding unpacking support. It can scan inside the following archives: ARJ, ZIP, MIME (+ all associated formats), MAPI (Outlook pst files), DBX (Outlook Express archives), RAR, TAR, GZIP, CAB, BZIP2, ZOO, ACE, ARC, LHA/LHX, TNEF (winmail.dat), CPIO, CHM, RPM, ISO, 7ZIP and SIS. It also supports a number of executable packers (such as PKLite, Diet, UPX, ASPack, PeShield, FSG, MEW etc.).
Resident protection (the real-time protection of the operating system), is one of the most important parts of an antivirus program today. avast! features a powerful resident module that is able to detect a virus before it has any chance to infect your computer. avast! Home Edition contains resident protection of the computer file system and a resident module for e-mails and news.
Avast features a module for the protection of IM (Instant Messaging, "chat") programs, and a module for the protection of P2P (peer-to-peer) programs. The list of supported IM and P2P programs is extensive with more than 30 programs currently supported.