How can I scan messages for viruses?

Virus scanning should be done in filter_end to inspect the fully assembled message. message_contains_virus calls every installed virus scanner (e.g. ClamAV) and returns the scanner name, the virus name, and a code ('ok', 'virus', or 'error').

use Mail::MIMEDefang::Antivirus;

sub filter_end {
    my($entity) = @_;

    my ($code, $category, $action) = message_contains_virus();

    if ($code eq 'virus') {
        md_syslog('Warning',
            "Virus detected in message from $sender ($RelayAddr): $category");
        md_graphdefang_log('virus', $category, $RelayAddr);
        return action_bounce("Message rejected: virus detected ($category)");
    }

    if ($code eq 'error') {
        md_syslog('Warning',
            "Virus scanner error for message from $sender: $category");
        # Tempfail on scanner error to avoid letting infected mail through
        return action_tempfail("Temporary error during virus scan, please try again");
    }
}