How do you detect malware in files?

Hello,

I’m considering your Sucuri plugin as a security solution for my website.

One of your features is a Malware Scanner. Can you clarify how you detect it? If it’s a database of malware signatures can it be efficient against modified malware files?

Also can you clarify whether you use any third-party service for such detection? I mean will my files be uploaded to third-party?