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My ISP is the largest in the country and known as SLT (Sri Lanka Telecom).

Through a single router/ADSL Modem, we have a small home network.

Lately, I see a message appearing from my ISP asking me if I want extended bandwidth and I just close it without responding. There's no pattern that I can figure out here that causes the message to appear.

But the most weird thing is that this is NOT a pop-up window. It seems like a DIV on my browser. There's nothing on my computer that could allow a third person to access my resources (at least I like to think so). My OS is Ubuntu 12.04 and the browser is FireFox.

Here's a typical example (most frequently experienced)...


  1. Open new tab on FireFox (FF).
  2. type the URL
  3. On top of the site, I see a DIV (not pop up window) that contains my ISP's message.
  4. The URL shows
  5. I close the message (using the x button that is part of the DIV)
  6. A brief message appears but it's too fast to read, and then the actual SO page comes up.

I'm starting to get suspicious and worried. This seems to happen on all computers on the network.

Thus my question:

Is this normal with the new technology or is this something to be worried about? I think this is like an opportunity for the ISP to do some free, non-solicited ads. But it could be more than that if they can control what appears on my page in place of the real thing. Is there something I can do?

The worst thing is that the question they ask can affect how I get billed. So if one of my kids respond to it, this can be a problem for me.

Thanks for your inputs!

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migrated from Aug 25 '13 at 14:13

This question came from our site for system and network administrators.

I think ServerFault is not the right place for this question, but as a very short answer: yes, your ISP can see/influence/modify everything you do over the connection you rent from them, unless the content is sufficiently encrypted or otherwise protected. In certain countries this 'ad injection' is considered illegal. – Sander Steffann Aug 25 '13 at 13:36
some consider this illegal? Huh, I feel invaded! And thanks for your input. Do you think there's something I can do to stop this sort of 'injection'? Setting up my own firewall wouldn't seem to be effective since this is from the ISP – itsols Aug 25 '13 at 13:41
itsols: I fully understand your feelings. I am lucky to live in a country (The Netherlands) where we have net neutrality laws which prohibit the blocking of Internet services, usage of deep packet inspection to track customer behaviour and otherwise filtering or manipulating network traffic. (wording comes from Wikipedia: – Sander Steffann Aug 25 '13 at 13:43
I would check if this happens on HTTPS sites as well, just out of curiocity – Journeyman Geek Aug 25 '13 at 14:47
up vote 2 down vote accepted

Yes, and pretty trivially. Many ISPs actually run your connection through a transparent proxy - this lets them do things like simple filtering (ours uses it for a limited blocklist) and caching. This also lets you, to an extent, alter the content of sites.

On a limited scale - an example would be here where they turn websites upside down or even blur them.

In fact the XKCD comic that article references

enter link description here

is PRETTY close to what's happening - your ISP is modifying your content.

As for getting around it, I suspect a little research and a clever adblock script should do the trick.

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Yes, it is possible.

In fact, we have seen this stateside in a few different forms.

This may or may not be legal, or explicitly illegal where you live. But it is certainly possible.

Using a third part DNS may remove the problem.

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Concur. HTML injection techniques have been around for awhile. You just need to be in "the path", which any ISP most certainly is. Using a third party DNS may or may not help, depending on if your ISP intercepts queries (e.g., to display ad pages when DNS queries fail). – joat Aug 25 '13 at 14:32

Changing your dns setting should fix this eg and also if you go to your providers web site somewhere berried in the millions of pages there should be a way to opt out of this behavior, if you opt out the will send you a cookie and if you loose that coolie you will have to do it all over again. Best bet is to just change your dns

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