Closed and Partly-Closed Systems

Here are some examples of closed and partly-closed systems:

• Closed systems on mobile phones 
  The operating systems in many basic mobile phones – as opposed to smartphones and phones that support the use of third-party, Java-based applications – provide an example of widely-used, protected systems.  These devices were not generally prone to virus attacks.  However, new applications could not be installed – so, the devices were severely limited in their functionality.

• Java virtual machine 
  The Java machine partly satisfies the ‘closed’ protection condition.  The machine runs Java applications in the ‘sandbox mode’ – which strictly controls all potentially hazardous actions that an application may try to execute.  For quite a long period, no ‘real’ viruses or Trojans – in the form of Java applications – have occurred.  The only exceptions have been ‘test viruses’ that were not particularly viable in real life.  Malicious Java applications generally only occur after the discovery of methods that bypass the security system that’s embedded into the Java machine.

• The Binary Runtime Environment for Wireless Mobile Platform (BREW MP) 
  The BREW platform is another example of an environment that is closed for viruses.  Mobile phones that run this platform will only allow the installation of certified applications with crypto signatures.  Although detailed documentation is published – to help third-party software producers to develop applications – the certified applications are only available from the mobile service providers.  Because each application has to be certified, this can slow down software development and delay the commercial release of new applications.  As a result, the BREW platform is not as widely used as some other platforms – and some other alternatives offer a much wider selection of applications for users to choose from.