Remove Joomla icon

Joomla is a very popular open-source content management software for web and it is estimated that about 2 % of websites in the world are running on it.  On some occassions, if I access a website running Joomla, the default Joomla icon is displayed in the address bar.  This is regarded as a security risk and bad guys  can launch attacks target at Joomla.  It is desirable to remove the icon (favicon.ico) and replace it with the organisation's or company's logo in an 16 x 16 icon size.