validate :validate_max_file_size, :validate_file_extension, **:virus_scan**

  # Scans the file for viruses
  def virus_scan

    # write to tmp file
    if @temp_file
      f = Tempfile.new('av')
      f.binmode
      if @temp_file.respond_to?(:read)
        buffer = ""
        while (buffer = @temp_file.read(8192))
          f.write(buffer)
        end
      else
        f.write(@temp_file)
      end

      # hand off to scanner
      f.flush
      result = %x[ /usr/local/bin/clamd-hook.sh #{f.path} ]
      if result.squish == "0"
        logger.info('virus detected, file rejected')
        errors.add(:base, 'Malware detected!')
      end

      f.close!

    end

  end