An important improvement of version 4 is also the possibility to repair infected files using so called Virus Recovery Database (VRDB). This database is generated automatically when the computer is idle (it can be set how often).
If a file is infected by a virus, avast! consults its data in VRDB and if the file does have。

如果文件被病毒感染损坏，而之前如果使用了VRDB功能那么可以恢复其原始状态。

我没用过AVAST
不过备份修复功能都会占用空间的
如果使用VRDB，在机子处于空闲的状态时会自动运行，也可设定让它在什么时候运行