You can use the Permissions option to change accessibility to files, or use the chmod command. Choose a password that is hard to guess and don't tell it to anyone. If you're a Unix user, look at the UCS's notes . Update this disk whenever software, hardware or a user is added or removed from the system. By default on the Teaching System, support for java and javascript are disabled.
More details are on CERT's page .
If you're putting files on the World Wide Web, read about WWW security CERT's WWW security page X windows Before trying to run X graphics programs remotely, read about Xauth security . Don't use xhost. For those registered as TechLink support contacts, Technical User Services has organised Workshops some of which are about security.