Below you will find links to instructions how to upgrade your shield. My recommendation is to
1) setup shield following the admin guide in either Router or Bridge mode.
2) make sure to activate the "advanced mode".
3) have a working SSH connection (dropbear instance setup)
4) and a working internet connection
Do NOT use Shield in [G]ateway mode - Itus has never fully developed this setup and not many users have reported it to work successfully!
Software & tools
While the browser interface (sometimes called LuCI) can handle most actions, you will probably need to transfer files or have command line access (also called CLI) using a SSH connection.
Please check the custom tools section on some commonly used software in combination with Shield.
Putty : Access to the command line (CLI)
WinSCP : Transfer files from/to shield, change access rights and file ownership
The development of Shield is not as mature as the over-the-counter solutions for a router/firewall/wifi that you can buy in Walmart or on Amazon. Sometimes Shield won't fully boot at all (= no web interface available), in that case a terminal cable in combination with Putty will help solving your problem.
Here is a link on how to buy a terminal cable: http://itus.accessinnov.com/Console-cable-411-td140.html
Upgrading Shield software
Originally ITUS released version 1.0 or RC2 on shipped devices. However they released a more stable version in November 2015, namely 1.51SP1. This should be your starting point for Shield.
The final key step is make sure that the detection filters are updated regularly. This is done via a script called fw_upgrade which needs to be replaced with a version that works without Itus. Please check fw_upgrade v8.2 for the latest version.
(Note: the link above may change due to active development. Please check for FW_Upgrade version 8.x recent postings by Roadrunner42 )
Shield has several tasks scheduled to update the time and the ISP filter definitions. Some of these tasks are scheduled too often (every 10 minutes) for no reason. These tasks are scheduled using a cronjob, if you want to learn more, please check here.
In LuCI go to System > Scheduled tasks you can replace it with the following:
Just to mention that the link for the FW_Upgrade_V8 is incorrect (takes you to Console cable page).
Also - I am running my Shield in Bridge mode, running 1.51 SP1. My IPS rules update every night (as confirmed on the Status page). Can I assume everything is ok, or do I need to do anything else to keep Shield doing it's job?
Sorry, just a little confused about what (if anything) MUST be done to keep this working. I'd rather not tinker unless absolutely necessary.