Symbian OS platform security, introduced in S60 3rd Edition, brings new levels of device and application security to the S60 platform. Basically, the applications which take advantage of the most-secure APIs, will have to apply for the Symbian Signed program, making the overall system much less vulnerable. Of course, many applications will not need platform security capabilities or will use those the customer can grant trust to.
Forum Nokia has launched a new page on Symbian OS security and Symbian Signed program wherefrom you can get all the information you need to make sure your application (in case you’re a developer) meets all the standards and doesn’t hurt the end-user.