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On Jun 8, 2021, at 02:07, CUVILLIEZ Jérôme via clamav-users <clamav-users@lists.clamav.net> wrote:
I would like to know how the signature database of ClamAV is build ? based on which signatures ?

I suggest you start by reading though this manual on Signature writing first: 
<https://www.clamav.net/documents/creating-signatures-for-clamav>.

It is also possible to write your own signatures and there are a few sources (e.g. https://sanesecurity.com/usage/signatures/) for additional "Unofficial" signatures that can be added should if you have the need.

-Al-