OK, I just missed that “by default” in the previous post :wink:

You are mostly right - the files in archives are not dangerous, and they would be detected when extracted. However, sometimes scanning of archives may have some sense… e.g. when scanning e-mails (e.g. on mail-servers, or even on home computer) - it makes it possible to delete the infected messages/attachments automatically even when they are compressed - without bothering the user (don’t forget that many user are likely to “panic” when they got a warning that they just received a virus!).

Of course, we are talking about “regular” archives, like ZIP, RAR, etc. Executable compressors are certainly different…