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I use a Zyxel P-660HN-T1A modem/residential gateway to connect to my home ADSL subscription.

I called my ISP today to inquire about upgrading to a faster broadband package. For some reason, my call was misinterpreted as a downstream speed complaint and my call was forwarded to a technician who carried out a BER test.

After doing this (and verifying that there were no issues), he mentioned the presence of 2 devices connected via WIFI and wanted to know if I knew about this as they might be downloading data unbeknownst to me. Of course, I was shocked at this.

Furthermore, he went on to suggest that I should secure my WLAN with a passphrase. I have unprotected WIFI for reasons of my own.

My obvious question: How did the tech support agent attain this information? Should we assume that the ISP has admin access to the device and is essentially on the local network at all times, despite me changing all default logins long ago (including the telnet login credentials)?

Please advise a concerned user.

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migrated from Jul 11 '13 at 20:02

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

The modem you have allows remote management via TR-069, which could allow access to the information mentioned.

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This is a good research start for me. Thank you! – synack Jul 11 '13 at 20:13
I'm not sure what Zyxel has implemented in that particular device, but you the specs are here – ernie Jul 11 '13 at 20:15

Did the ISP provide the router? If yes, then it is their equipment, why wouldn't they have access. I know for certain, that Comcast and other ISPs have access to the routers they provide.

If you are paranoid, you should set the ISP provided equipment to act as a bridge, and get your own router.

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Thanks for your input. Yes, they provided it. I would like to know how they access it and how I should investigate that. Also, if I buy my own modem/router will this be a non-issue? – synack Jul 11 '13 at 20:11
I don't know for your router/ISP. It would probably be though ssh or a web interface. – Zoredache Jul 11 '13 at 20:14
Comcast doesn't allow CMs they can't control. Even customer owned equipment is managed by them. I couldn't say definitively for other ISPs, but I'm sure it's common practice. – Chris S Jul 11 '13 at 20:17

It's common for ISPs to have full access to the CPE.
This is usually the "modem" and anything integrated into that device.

If you don't trust them for any reason I strongly suggest limiting the functions provided by the "modem" and attaching whatever equipment you supply to it (eg, modem plugged into a WiFi router).

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Thanks Chris, would you mind explaining how they might be accessing it (over IP, or somehow over analog DSL)? – synack Jul 11 '13 at 20:10
DSL is digital, that's what the "D" stands for. Every system I've seen is based in SNMP or TR-069. – Chris S Jul 11 '13 at 20:15
DSL, yes. But this is a DSL modem/gateway that sends/modulates the signal out across POTS. Therefore, analog. – synack Jul 11 '13 at 20:20
ADSL uses OFDM modulation, but I wouldn't consider that Analog... unless you also consider WiFi, Cellphones, and Bluetooth to be "analog" too. – Chris S Jul 11 '13 at 20:29

yeah they do, but its contained. It's not like they have access to your internal network or something outlandish.

He asked you if you had a secured wifi network with the logic that un authenticated users could be eating up your bandwidth. There's really no way for him to enumerate this info via a single remote connection to the modem.

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My apologies if it wasn't clear, but I didn't mention anything about having unprotected WIFI. – synack Jul 11 '13 at 20:09
yes you did. "Furthermore, he went on to suggest that I should secure my WLAN with a passphrase. I have unprotected WIFI for reasons of my own." It seemed as if you thought he somehow knew you had un protected wifi when he was only making a logical guess that someone could be on your network eating bandwidth. It's also very commonplace for UPNP routers to know about other devices they are connected to. – Scandalist Jul 11 '13 at 20:13
You're misunderstanding, unfortunately. Verbatim, his words were: "Oh, you should also probably secure your WIFI with a passphrase in case those connected devices are your neighbours'. Do you know how to do this?" This was prior to me mentioning anything about open WIFI. Thanks for your input. – synack Jul 11 '13 at 20:16
I'm only going off what you said in your post, where you yourself mentioned having open wifi. We cannot mind read here at SU. In any case, there's no way for him to access your internal network or resources short of installing a VPN and violating some kind of privacy agreement. – Scandalist Jul 11 '13 at 20:21
@Scandalist That's fine. Most of my traffic goes through an encrypted tunnel to a VPS my colleague hosts for me. The obvious concern is that the Linux distribution (I'm almost sure it's a Gentoo variant) can be controlled in totality. That includes the ability to install packages and probe the network. You probably don't need me to explain why that's bad. Thanks for your input on my question. – synack Jul 11 '13 at 20:31

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