Are you using your own equipment (modem and router, or a combination of the two), or comcast's?
So, I'm not sure what level user you are, so I'm just going to break this down as if it's something you've never done before. I apologize if any of the information isn't new to you and you know what you're doing. I don't mean to sound condescending, I just want to make sure I'm being as easily understandable as possible just in case. 🙂
If the issue isn't related to Comcast botching something up, which isn't outside the realm of possability, other things that can cause this are:
- Someone in your house who's using your network is using or used a TON of data and wasn't upfront/honest about it. (Or they just didn't know that what they were doing or downloading was really that data-heavy.)
- Some kind of malware or trojan on your computer - A legitimate program that you or someone downloaded on one of your devices that is constantly sending and receiving large volumes of data (sometimes things like this can be disabled, other times it could be something nefarious built into a program like cryptojacking that tries to run in the background).
- Torrenting and filesharing on a P2P network. (Related tot he first point.)
- Your network password has been compromised and someone else nearby is using your internet for who knows what.
The first (and most simple) thing to try is changing your network's password. Go into the router via your internet browser. Type in the nav bar one of the following: 10.0.0.1 , 192.168.0.1 , or 192.168.1.1 . These, or a similar iteration using the first three sets of numbers with a different final number in the address, are the most common default IP addresses for home routers. (At least in the ones I've used or came across. Two others that are possible on Comcast routers are 192.168.100.1 and 10.1.10.1 .) If those don't work, do a google search for the default IP for a Comcast router. If you got the address right, you should get prompted for a username and password. The default username is typically "admin" or "Admin" for the overwhelming majority of routers out there, and if I recall Comcast doesn't let you change that if you're using their equipment. The password is either on the side of your router or set to a default such as "password" (which is common for most routers to actually get into the router). If you're using a 3rd party router, you can usually just google the default username and password for you particular router model if the ones mentioned don't work and there isn't anything physically on your router itself that says what the defaults are.
Once you're in the router, you should be able to access the wireless/WAN settings to change the password to your network. (You can change the network name too if you'd like, but the password is far more relevant.) Also, change the password to actually access the router itself. The second part will likely be in a different tab, usually under "advanced" or "administration". Be sure to include a captial letter, a number, and one special character. This also applies to the network password as well. (It doesn't have to be anything needlessly complex. Something like "MrPoopyButt1!" or "[yourFirstInitialLastNameWithACaptialLetter]1!" is perfectly fine.) Avoid single words or common last names as those are ridiculously easy to brute force into. On a side note, XKCD actually has a great comic strip on password security that's worthwhile and simplifies the "why" if you've never seen it before. Next, since you're in the router, there's a couple of things that you can disable that can help mitigate possible malware and others from hijacking your network. (I forget whether or not both of these next two things are possible on Comcast's rental equipment, but they are on the majority of routers out there, so we'll treat it like they are.)
1. Look for something called "WPS". This is usually under the tab that deals with the wireless network, but results may vary. WPS, while convenient for some things (It's like a wireless quick connect most commonly used for printers, but can be used for other devices), is a pretty well known and easily cracked vulnerability. Disable it. (If you need to connect some device later on that wants you to use it, there's pretty much always an option to manually connect to a wireless network, and the process is pretty straightforward.)
2. Look for something called UPnP and disable it if it's on. Some types of malware/trojans/etc. can use this to bypass the network firewall. In most cases it's typically not needed for a home network. In the cases where something is utilizing UPnP and needs port forwarding, there's tons of tutorials available on how to do this. (It can look complex at first, but the reality is that it's actually pretty simple once you see what's going on.) If you suddenly start having problems with certain programs or devices, such as P2P or VoIP applications, you can either turn UPnP back on or go through a couple of steps within the router to get them working again. (Again, there's a bunch of online tutorials on how to do that if you want to elect to keep UPnP off.)
For kicks and giggles, once you're in the router, see if you can look for a list of attached devices in the interface. If you can, take a look at what devices are on your network. Some devices will have obscure names and some wont, so you may not recognize some (or most) of them. The idea here is to see if there's someone piggybacking on your connection. If you can positively identify a connection or MAC address that you know is not in your apartment, you can try to block that device. (Sometimes the option to block a device is in a different tab/menu alltogether labeled as access control or something similar.) This aside, you should still turn off WPS and UPnP anyway.
So this turned into a novel, but hopefully it helps. 🙂
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