Sudden huge increase in internet data usage

I am experiencing the same - clearly a Comcast issue and yes, perhaps intentional on their part

My overage from Dec for 200MB just showed up on my bill. I called customer service through the website and asked for credit .. I was direct and short but not rude. They asked if this was the first time I was charged, which is correct, so they provided the "one-time" credit immediately. I got confirmation by email immediately as well.

Meanwhile, I have turned off wifi on the cable modem, channeling input into Amazon eero home network setup, subscribed to $30 per year eero secure plan that gives me control over every device at home and real-time analytics, historical usage charts for each device or groups of devices by day, week, month etc. I am now able to set schedules for my kids devices, cut-off internet to router etc, dynamically setup guest networks and more. Also eero blocks popup ads and many other internet perils before they reach my devices. Given the hacking, phishing, ransomware etc, $30 per year is a low price to pay for this much of benefit.

Something good came out of this bitter experience. I'd suggest everyone turn lemon into lemonade and take control of your online life. Best wishes.

I saw in other threads that people were having the same problem as me, but it looks like they were helped by private messages. Just last week, I got a notice that I had exceeded my 1229 GB of data for the month. It was only the 17th of the month, but I had already used twice as much data as I typically use in a month. I worked with agents to reset and rename my network and change my password. I did look and find a few devices that I didn't know and got rid of them Even now, although it has slowed down some, I still seem to be burning through more data than would seem possible. I really need some help figuring this out.

This month, first time ever I also received alert about exceeding my 1225 gb plan. 
usually don’t even come close and only change was went from 200 speed to 300 speed.. can’t get any help answering why from Xfinity rep… they simply do not care.

Obviously another way to overcharge for subpar services

I’m having the same issue. How my family of three is now over 1.2 Tb makes zero since. Interesting how it has become a common issue with many people. I want to see what my daily usage is so I can problem solve.

Hi, Why do I keep getting notified that I have used 75% of my internet data, then 90% a couple days later, when I haven't been home in over a week to use my home internet?? 

February is showing a doubling of usage . Nothing has changed usage wise . Checked connections through router and no huge users . 
The Xfinity app shows me  using an Arris T6862G  modem where I actually have a SB6121.

Helluva time getting to a human contact.

I have had the same issue. Exceeded my monthly limit yesterday. Initially I blamed my kids for too much streaming. However when I did some internet sleuthing, I saw someone mention issues with excessive data usage with the Amazon Firestick. I have one tv that uses the firestick, but we hadn’t used it for weeks. But I checked the data monitoring details on the firestick menu, and lo and behold, the Xfinity Stream app used 1.2TB this month alone!!!  That is with the tv and firestick seemingly off. I haven’t followed up with Amazon or Comcast yet as I just found this out this afternoon, but I thought I’d put out there what I found in case anyone else has the same issue. I unplugged the tv with the firestick for now until I can be sure it won’t happen again. 

Our usage since August has been 577gb, 698gb, 304 gb, 623gb, 576gb, 498gb and now that it’s just 2 people in the house and no change in our internet using habits, our data has shot up to 1117gb with 5 days remaining in the month. Chatted with an agent but he had no idea what was causing this spike but did tell me that the average daily usage in February has been 50-60 gbs except 2 days when it went up to 165gb and 145 gb. No reason for these spikes. I have no idea what is going on. I just know that our internet usage should go down as it did in January not more than double as we are one person less in our household since January

I had the same problem and it seemed to improve after I changed my router password.       Probably a good thing to do periodically anyway.   Then I monitored my usage a couple of times a day to ensure I did not exceed the monthly limit.   

OMG, what is going on with Xfinity?  I, too, typically used about 600-700 per month, and since December 2021 I am getting emails and phone messages that I am about to go over the cap by the 17th of the month.  I was on the phone with them for 2+ hours in January, they couldn't tell me why this was happening.  They said it's because I work from home, which I have been doing for 10+ years, so they got no joy there.  Then they said my equipment was old and I should take it down to the local Xfinity store and change it out for a new one.  OK, done.  Thought that would help, but the 17th of Feb, I get a message that I used 75% of my data.  Now on the 24th, I get a message that I used 90%.  What gives?  I live alone, I have all my streaming devices set at 720, I turn off the WIFI on every device I am not directly in front of, I turned the Bluetooth off on everything, but alas, still burning through data like a house afire.  Considering the number of complaints on here, I would think it in their best interest to address this formally.   When a suitable replacement comes to my area, I will be dropping Xfinity immediately.

I am ready to switch now! In my area it's either xfinity or Ziply. I will tell you soon when I switch.

Same issue. Consistently used 600-700 a month for two years while working from home and already over 1500 for February a shorter month. Spoke with their data team, “try resetting your password” was the advice. Slowly brought back on devices like laptop, smart tv. Been able to loosely figure out that according to Xfinity data, streaming on Netflix takes 20-36gb an hr which is unrealistic and severely overstated. Still haven’t added our phones to the internet yet. Who knows what changed on their end but seems like lots of people having same issues so it’s a Xfinity problem.

Yes, I've run into the same problem. I think they are calculating larger data usage even though we haven't changed our streaming usage to get us to sign up for the unlimited program and pay them more money. It's robbery based on made-up data.

I'm also having this same issue. Before November I was not having this issue, but for November, January, and now February I'm being told that I'm using my data and then some. I've been teaching from home using Zoom from 9-3 each week day since September and didn't have any data issues until November. Xfinity, this is a serious issue that I can see a lot of other people are dealing with. My most recent chats kept pushing the unlimited data, which is frustrating.