ClamAV

ClamAV is open-source security software used for malware and antivirus.

ClamAV can be called automatically by Amavisd-new as an SMTP filter for email delivery.

On a modern Ubuntu system you can install ClamAV like so.

sudo apt install clamav clamav-freshclam

ClamAV is updated by using freshclam.

Enable the freshclam service which is disabled by default. This will ensure your signatures are kept up-to-date.

sudo systemctl enable clamav-freshclam
sudo systemctl start clamav-freshclam

You can check on the freshclam status like this, to make sure it's okay.

sudo systemctl status clamav-freshclam

Use sigtool to list all the signatures in the clam database.

sigtool -l