来自捷克的Avast!，已有17年的历史，它在国外市场一直处于领先地位。Avast!的实时监控功能十分强大，它拥有七大防护模块：网络防火墙防护、标准的本地文件读取防护、网页防护、即时通讯软件防护、邮件收发防护、P2P软件防护。这么完善的防护系统，定能让你的系统练就一副金刚不坏之身！任意开启各项保护模块能够查杀流氓软件。

Changes in Version 4.8.1169 (March 29, 2008):
* avast! now contains a built-in anti-rootkit protection
* avast! now comes with a built-in anti-spyware protection
* new self-defense function to prevent active malware from terminating avast! processes as well as corrupting avast! files and registry items
* scanners now display a progress of current scan (percentage of work done)
* fixed a vulnerability in AavmKer4.sys kernel-mode driver (problem applies to Windows NT/2000/XP, 32-bit only); special thanks to Tobias Klein
* improvements in boot-time scanner (detection & removal of hidden or hard to delete files)
* boot-time scanner will not start when booting into Safe Mode (the program was "invisible" in that case, no progress/messages could be seen)
* improvements in many unpackers
* ACE and RAR unpackers now work even in boot-time scanner
* IM Shield: added support for QQ
* improvements in handling of NTFS streams
* Internet Mail provider now displays the name of the sending/receiving program in the tooltip of its taskbar icon
* implemented a protection against false positives in critical system files
* removed a small memory leak in one of avast! drivers (Windows vista and XP 64-bit only)
* added support for 64-bit WHS connector (available in WHS Power Pack 1)
* greatly improved performance of the uPDAter, especially in cases where many increments are being downloaded (e.g. avast! installations with outdated virus definitions)
* silent installation now also includes scheduled tasks, if any
* resolved a compatibility issue with Acronis TrueImage (XP 64-bit only)
* compatibility tests with vista SP1 and XP SP3