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Privileged operations should be limited to the smallest possible code blocks that require such privileges. The Java AccessController mechanism allows only certain parts of code to acquire elevated privileges. When a class needs to assert its privileges, it executes the privileged code in a doPrivileged block. The AccessController mechanism works in conjunction with the security policy in effect. Because users may be unaware of the details of the security model and incapable of correctly configuring security policies tailored to their requirements, privileged code present within the doPrivileged blocks must be kept to a minimum to avoid security vulnerabilities.

Security Manager

A security manager is an object that defines a security policy for Java code. This policy specifies actions that are unsafe or sensitive. Any actions not allowed by the security policy cause a SecurityException to be thrown. Code can also query its security manager to discover which actions are allowed. The security manager can also be used to control the functions the trusted Java API can perform. When untrusted code should be disallowed from accessing system classes, it should be granted specific permissions to prevent it from accessing trusted classes in the specified packages. The accessClassInPackage permission provides the required functionality.

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