If we remember where an applet originates, we can deny or permit access based on previous applets from the same location. In addition, a digital signature included within the applet can guarantee its validity. Java is capable of using digital signatures to verify content during the download. JAR files are single files containing all class files and images and resources. A much better alternative to client-side protection against Java applets is to secure your network's access points.
Most corporate networks employ firewalls to guard against unauthorized traffic.
However, a firewall alone will not protect your clients from requesting corrupt or hostile Java applets. With the addition of software at the firewall, it is possible to inspect Java content as it enters your network. This strategy will depend on the firewall vendor and your network's configuration. With certain software, an administrator can allow or deny specific access to the network based on an applet's origin. Additionally, the administrator can restrict access to an applet based on its digital signatures or author information.