Updating firmware on modem
Now, its important to not confuse the cable modem with the router/firewall gateway device, in most circumstances these are two different pieces (the modem is strictly responsible for providing IP/ethernet connectivity over the coax, nothing more) so a much different answer would apply if you ask the same question about your router/firewall device.
This is going to depend on your ISP - it isn't something that we can definitively say. If you are concerned about the security of this device (which is great) or are concerned about the integrity of the ISPs network (or about anything the ISP might do, like inserting ads or messages into http traffic), my advice would be to first ensure there is hardware you own between your devices and the cable modem and to ensure that that hardware has good passwords and is kept up to date - product recommendations are off topic here, but there are some good open source router firmware replacements out there that might be more reliable and secure than factory default ones.
As it reboots, it will check that it is running the latest code approved by your service provider, and if not, will download the latest version.
It currently has firmware version SB4100-0.4.4.3-SCM01-NOSH, but there is a newer firmware revision, SB4100-0.4.4.5-SCM01-NOSH that was the last one for the SB4100's.1. Your ISP is the one who can do so - if it's the one their currently using with the cable modems used on their network. If there is any available, you'd probably gotten the update already - or you can try calling to see if there is one available that they can load automatically into your modem. It currently has firmware version SB4100-0.4.4.3-SCM01-NOSH, but there is a newer firmware revision, SB4100-0.4.4.5-SCM01-NOSH that was the last one for the SB4100's.1. Isn't there a software utility available anywhere that lets the end user do it?
If you have, congratulations, you can stop reading this article right now, if not, read on.
Your router’s firmware is basically the operating system that is specifically designed to run on your specific make and model of router (unless you are using a multi-router compatible open source firmware such as DD-WRT).
If you're using an Apple Air Port router, you can use the Air Port Utility program to check for updates.
One good reason why your router manufacturer may put out a firmware update is because they are trying to fix a vulnerability that was detected in the current firmware, updated firmware is similar to system updates (as in Microsoft’s Windows Update).
As bugs are found and corrected, updated firmware is released.
Router manufacturers may also issue a firmware update to upgrade features such as outdated encryption modules or they might add entirely new security mechanisms that weren’t in previous versions of the firmware.
Besides security fixes, your router manufacturer may have found a way to enhance your router’s overall performance, which is always a good thing.
There is no way for an end-user to update cable modem firmware.