Untrusted applets are Java applets that have limited permissions and cannot perform certain operations that could compromise the security of the system where they are executed. These applets are typically downloaded from the internet and run within a restricted environment, often referred to as a "sandbox," which limits their capabilities to interact with the system.
By default, all Java applets downloaded from the internet are considered untrusted. This classification is crucial for protecting the user's system against potentially harmful actions. Untrusted applets are restricted in several ways:
File Access: They cannot read or write files on the host file system[1][3].
System Access: They are prohibited from accessing system properties or executing system processes[1][3].
Network Restrictions: They can only establish network connections back to the originating server[3].
Execution Environment: They run under the supervision of a security manager that enforces these restrictions[1][3].
The security model for applets includes various mechanisms to ensure that these restrictions are enforced. For instance, the applet classloader and the security manager play critical roles in maintaining the security boundaries for untrusted applets. The classloader ensures that applets are loaded in a secure manner, maintaining a strict separation between the applet's code and the local system's code. The security manager enforces the sandbox restrictions, preventing the applet from performing actions that could be security risks[1].
Moreover, the bytecode verifier checks the code of untrusted applets to ensure that it adheres to Java's language specifications and does not perform operations that are out of bounds, such as stack overflows or unauthorized memory access[1].
In summary, untrusted applets are Java applets that are run with limited permissions to preven...
