Networking, Firewall, Mostly Closed + Remote Administration + UI Group Details

Summary

The Mostly Closed + Remote Administration + UI firewall group is designed for web or email servers, allowing access to those services without being fully exposed to the Internet. It can be too permissive for some desktop systems, and too restrictive for other types of servers.

The difference between the Mostly Closed group and a group with the +RA identifier is that this group allows users and administrators to remotely administer the computer from off campus.

Note, in 2017 the Chief Privacy and Information Security Officer placed significant restrictions on inbound traffic for Remote Administration services.  As such, the only remaining ports allowed by the +RA modifier are ports 3283 and 5988.

The difference between other groups and a group with the +UI identifier is that this group places no restrictions on network traffic between the University of Illinois campuses.

Internet: Services allowed in

From computers that are not part of the University network:

Like the Mostly Closed group, HTTP, HTTPS, IMAP, secure IMAP, POP3, secure POP, FTP, SFTP, SMTP, and H.323 are allowed. (A specific port list is available.)

Assuming that a machine uses the standard ports for its services, placement in this group means that users from outside the firewall will be allowed to initiate connections with encrypted and unencrypted web servers, mail servers, FTP sessions, and voice-over-IP connections on machines in this group. However, no other services will be accessible to outside users if a machine is in this group.

Internet: Services allowed out

To computers that are not part of the University network:

All (except the ports that are always blocked in both directions)

Advantages

• Computers in this group are at lower risk from attacks from outside the university on the ports that are blocked.
• Users still get access to Internet for services they already have.
• Popular services are still accessible from outside (for example, departmental web servers, mail servers, etc.).
• Power users and administrators can access the computer from outside the firewall for administration purposes.

Disadvantages

• Computers are still at risk for any attacks coming through the ports that are open. Examples include web server vulnerabilities, sendmail vulnerabilities, etc. Note that many non-web-server devices now have interfaces that use web ports; some of the vulnerabilities that target web ports will cause problems in these devices. For example, HP JetDirect printers could be made to print out extra pages because of a web server vulnerability.
• If a computer is offering services that require additional ports, this package will not work for that machine.