avast! Free Antivirus 是一款免費的防毒軟體，但功能上可是一點也不遜色，它擁有一個幾近 100% 的完全防護功能，不論是檔案、電子郵件，甚至是 P2P 以及 IM 軟體，均能受到它的防護；此外，無論是電腦系統安全、網路安全或網頁，也一樣都能受到它嚴密的保護。
不過，這款軟體雖是一款免費防毒軟體，但在未註冊取得軟體註冊碼之前僅能試用 60 天。在註冊取得註冊碼之後，將可透過電子郵件信箱免費獲得一個一年有效期的註冊碼。當該註冊超過有效期限後，必須重新註冊取得另一組新的軟體註冊碼，但註冊是免費的。
avast! Free Antivirus 2015 繁體中文註冊頁面
※注意：這款免費軟體綑綁您可能不需要的程式 (免費軟體開發者常見的獲利方式)，在安裝時會顯示安裝第三方軟體的選項。第三方軟體包括根本用不到的工具列及其他垃圾軟體、它們可能會更改瀏覽器首頁 (首頁綁架)、預設的搜尋引擎及其他相關軟體的設定，因此在安裝過程中一定要看清楚，務必取消勾選安裝第三方軟體的選項。
§ 作業系統：Windows 2000/XP/Vista/7/8/10 (32 & 64 位元)
§ 官方網站下載頁面
§ 檔案下載
avast! Free Antivirus 原文簡介：
Avast! is a package of applications that aim to protect your computer from a possible virus infection or other malware threat. If you use it correctly, and in combination with other programs such as data backup utilities, it will significantly reduce the risk of your computer being attacked or infected by a virus, and thus the risk of losing important or private data.
Based on the award-winning avast! antivirus engine, avast! antivirus contains all of the features you would expect in a modern antivirus program. It incorporates anti-spyware technology certified by West Coast Labs’ Checkmark process, as well as anti-rootkit and strong self-protection capabilities, but now provides even faster scanning with improved detection ability. It contains several real-time “Shields" which continuously monitor your email and internet connections and check the files on your computer whenever they are opened or closed.