I have cable from Time Warner and a "modem" they supplied. No other devices, or WiFi.
Actually, you should be able to have WiFi with the modem. Anyway, before I go over this please remember you can screw up your modem by randomly changing settings. Time Warner modems are set up to provide DHCP which gives your computers addresses and they act as routers. They do have a firewall.
To look at all that try this:
Open a browser (Safari is fine) and in the address area type: 192.168.0.1 -> this should prompt your modem to ask for a username and password. If you have the motorola modem that Time Warner usually uses, the defaults are username: admin password: motorola
If you have changed those go ahead and put in the ones that these were changed to.
I will tell you that it is possible the ip address is not what I have above. If the above does not work look at the ip address you have one your Mac and then try the first 3 sets of numbers adding 1 or 0 or 254 at the end: xxx.xxx.xxx.1 or xxx.xxx.xxx.0 or xxx.xxx.xxx.254 It is usually one of these.
Once you get in you can browse but remember don't go randomly changing stuff.
I would strongly suggest you google the manufacturer and model number of your modem and download the users guide. That will have all kinds of information in it. You can set access permissions, firewall settings, a whole host of stuff.
Most people just plug and play when it comes to what their provider sends them. I have done numerous home network repairs using the default passwords to get into their modem/router etc. Most people do not know that once in, I can see and or change the access passwords, change any setting I want how ever I want. Default passwords that access the modem should always be changed.
Lisa
Okay just saw your post on your model. Looks like the access ip is 192.168.100.1. Having now read the manual on your modem it seems very basic. You might consider getting a good router with a firewall. I don't see one that is configurable in the setup manual. Interesting, it could be the manual is rather lacking. Anyway, try checking it out.