How to Prevent your ISP from Controlling your SOHO Router (TR-069)

I freaked out a bit a lot when learning about TR-069 from Shahar Tal's great talk at this year's area41 security conference. Basically, if your router features this interface, your ISP can do all sorts of things like read and alter the configuration but also upgrade the firmware without your knowing.
Being a Swisscom client, I use a Centro Piccolo aka Motorola Netopia 7640 VDSL Modem. I knew that there had to be some kind of remote management, e.g. since resetting the router password is done via the the Swisscom customer website instead of directly on the router's administration interface. Then, there is no obvious configuration option refering to TR-069 nor CWMP in the admin interface. But: you can access extended settings by telneting the router. Here's the menu options you have to select to disable CWMP:

$ telnet 192.168.1.1
Trying 192.168.1.1...
Connected to dsldevice.home.
Escape character is '^]'.

login: admin
Password: **********

Terminal shell v1.0
Copyright (C) 2011 Motorola, Inc.  All rights reserved.
Motorola Netopia Model 7640-47 Annex A VDSL2 IAD
Running Netopia SOC OS version 9.0.10 (build h2d8)
ADSL/VDSL capable
(admin completed login: Admin account with read/write access.)

Centro_piccolo> configure

Config Mode v1.3
Centro_piccolo (top)>> management cwmp
Centro_piccolo (management cwmp)>> view
    cwmp
      enable on
      acs-url "https://rms.bluewin.ch:8443/cwmpWeb/CPEMgt"
      acs-username "********************************"
      acs-password "********************************"
Centro_piccolo (management cwmp)>> enable
Centro_piccolo (management cwmp enable)>> set
      enable (on) [ off | on ]: off

Here you can also see the URL of the ACS (the ISP's configuration server). Save before quitting, you should be then safe from any snooping from your ISP. Oh, and while you're at it, try the undocumented magic command in the telnet prompt ;-)