Are you using Safari to surf the Web? If so, open preferences in Safari and the General Tab. Be sure "Open Safe Files after Download" is NOT checked.
As a follow up action, you can also exclude your download folder from your backups .... that way the malware file sitting there idle in your downloads folder is not backed up.
Just a thought.
Cheers ... McBie
Wow, that's a really good idea. Never thought of that. How would I do that? I opened Time Machine preferences, but I couldn't see how to do it.
Open up time machine preferences, click the lock and enter your password, select options.
A dialogue box opens up, click the + and select your downloads folder from the window that pops up.