These code fragments are called applets.
Information servers can customize the presentation of their content with server supplied code.
But this increased power for Web applications is also a potential security problem. The Java security model and flaws arising from implementation errors, loopholes in the security model and unintended interaction between browser features are examined in this chapter. The language features for security, the low level security mechanisms through compile time checking, the ClassLoader and the SecurityManager are described. Some simple examples of hostile applets are shown to illustrate some of these attacks. The chapter concludes with some future directions that Java security model and implementation might take to make it a more secure environment to accomadate the openness desired by Web application writers and the security needs of their users.