We help IT Professionals succeed at work.

Question in security if a stranger connects physically to a private internet cable

Medium Priority
174 Views
Last Modified: 2019-07-13
In a conversation in a get together last night, it was stated that if an outside person illegally connects to ones internet cable line (that is cut and attach to main line that connects to ones’  home), will be able to see everything one navigate to.  I understand that it doesn’t work like, by connecting to ones Wi-Fi they can spy on one, etc.   But the person said a bunch of tech words so I wanted to know what EE has to say.  Can a person by connecting to ones cable line have access to ones web access and see all?

Thank u.
Comment
Watch Question

JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
No.  They may be able to attach a modem of their own, but other modems are on that line anyway (cable is a shared resource) so they cannot get into your modem unless they have the credentials to do so. That is most unlikely, so no.
CERTIFIED EXPERT

Commented:
It’s technically possible to record the modems modulated analog audio signal and to glean unencrypted information from it.  When used for faxing, for example, there is a test tool called fax_decode which takes a one channel audio wave file and decodes from it a fax bitmap into a tiff image file.

This tool is part of the SpanDSP library from soft-switch project. You can download it from https://www.soft-switch.org/downloads/spandsp/

Also see https://www.vocal.com/fax-modem/fax-demodulator-fax-decoder/
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
Most transmissions (https, email) are encrypted now, so that would probably have limited use (so far a I can see)
CERTIFIED EXPERT

Commented:
Agree with John that most traffic is encrypted today. Somewhere I read that some ISP providers use also VPN over the DSL between them costumers.

This is the only post I could find. It says it is possible, but I'm not sure if it is trustworthy:
https://security-assessment.com/files/documents/news/20.11.2009%20Security-Assessment%20Uncovers%20DSL%20Vulnerabilities.pdf
CERTIFIED EXPERT

Commented:
... will be able to see everything one navigate to.

You'd need a modem to view the TCP/IP traffic.  Anyone on the same cable can view the sites you visit, but not any https encrypted content.

Some sites give out a lot of information in the link.  For example, experts-exchange gives the question subject as part of the unencrypted link.

htt p s://w w w.experts-exchange.c o m/questions/29151863/Question-in-security-if-a-stranger-connects-physically-to-a-private-internet-cable.html

Some sites use CDNs and hide even that data.

Someone can use all the links you visit to correlate activity.  Those links are the metadata.  Enough metadata can still be used to paint a picture of your activities.  Sometimes that's enough to pierce someone's veil of privacy.
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
You'd need a modem to view the TCP/IP traffic.  Anyone on the same cable can view the sites you visit, but not any https encrypted content

Yes and (1) lots of shared traffic from numerous existing modems of the line,  (2) it would be exceedingly difficult to separate the cable TV, phone, and internet signals.
Security Officer
CERTIFIED EXPERT
Commented:
Several things come I to play:

  1. Cutting the wire and inserting a splitter on the line results in signal loss which could be detected by the ISP or you.
  2. Even adding their own cable modem won't help as it isn't going to be registered by the ISP so no traffic will go through.
  3. Even if it does connect, think about how cable works.  Several houses share the cable line yet don't see each others traffic.  They would not know what channels are assigned to your cable modem.

To see traffic on the wire they would need to tap into your router or wired network.
JohnBusiness Consultant (Owner)
Most Valuable Expert 2012
Expert of the Year 2018

Commented:
Jana  -- 99.9% No   0.01% maybe possibly.   Ordinary Normal Distribution in Life (always true)

Author

Commented:
Kevin, that is what i meant "Cutting the wire and inserting a splitter" but couldn't get wording right.  I spoke with the ISP prior checking on the question is exactly as you said: "... adding their own cable modem won't help as it isn't going to be registered by the ISP so no traffic will go through.... channels assigned to cable modem will not be known ... To see traffic on the wire they would need to tap into your router or wired network."