How to auto reset Fiddler when 'system proxy was changed'

17 posts, 0 answers
  1. Alex
    Alex avatar
    1 posts
    Member since:
    Jun 2012

    Posted 02 Mar 2014 Link to this post

    From time to time, sometimes a few times a day, Fiddler would show a yellow bar and a message "The system proxy was changed. Click to reenable Fiddler capture".
    Is there a way to make the re-enabling happen automatically? 
    I just want Fiddler always running so I don't have to re-enable it.

    Thanks.
  2. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 05 Mar 2014 Link to this post

    Hi, Alex--

    To reestablish Fiddler as the system's default proxy, you must click the yellow bar. To avoid having to click the bar, your best bet is to determine what other application is changing your system's proxy settings and disable it from doing so (VPN software and firewall clients like ISA/TMG are common culprits).



    Fiddler does not automatically attempt to reestablish itself as the proxy as this could lead to an infinite loop, whereby it and the other software "fight" over the proxy setting in an endless loop.



    -Eric

  3. a.ateeque
    a.ateeque avatar
    1 posts
    Member since:
    Apr 2014

    Posted 09 Apr 2014 in reply to Eric Lawrence Link to this post

    Hi Eric
    I am facing the same problem.
    Is there any way to figure out what other applications may be changing the proxy settings? Can the client's proxy config be changed by a remote application?
    Thanks!
  4. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 09 Apr 2014 Link to this post

    Generally speaking, no, remote applications cannot change your local system's proxy settings, unless the remote application has a client on your computer. For instance, if your company uses Group Policy or login scripts, those can write to the system's registry using code on your local computer.

    If you don't have any programs known to change the system proxy installed (e.g. ProxySwitchers, ISA Firewall Client, TMG Firewall client, etc) then your best bet would be to download Process Monitor from SysInternals and set a filter for registry WRITEs where the path contains PROXYSERVER. This will show you all writes to the proxy server registry key, which will help you determine which process is changing the proxy behind your back.

    Regards,
    Eric Lawrence
    Telerik
     

    Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.

     
  5. André
    André avatar
    2 posts
    Member since:
    Dec 2014

    Posted 02 Dec 2014 Link to this post

    I have this problem too such a degree that fiddler is useless... The error comes up every other second and when I reenable Fiddler capture it takes maximum 1 sec before the message is there again. 

    I have tried to turn off everything I can think off as well as trying to monitor all changes to PROXYSERVER with Process Monitor. 

    What more can I do!?
  6. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 02 Dec 2014 Link to this post

    Unfortunately, unless you find the software changing your settings, you can't resolve this.

    Let's step back a bit though... when the notification appears, don't click it. Instead, click Tools > WinINET Options. Click the "LAN SETTINGS" button on the CONNECTIONS tab.

    What are the contents of this screen, and, if it's enabled, the contents of the screen shown when the Advanced button is clicked?

    Regards,
    Eric Lawrence
    Telerik
     

    Check out the Telerik Platform - the only platform that combines a rich set of UI tools with powerful cloud services to develop web, hybrid and native mobile apps.

     
  7. André
    André avatar
    2 posts
    Member since:
    Dec 2014

    Posted 03 Dec 2014 in reply to Eric Lawrence Link to this post

    My process monitor wasn't configured properly. When I experimented with it for a while I managed to find out that it was a Wajam application that was writing constantly to the proxy. So removing it solved the issue. 

    Thanks for this thread!
  8. Screw
    Screw avatar
    1 posts
    Member since:
    Sep 2014

    Posted 19 Feb 2015 Link to this post

    My VPN client (Big IP Edge Client, F5 Networks) keeps doing this. I cannot use Fiddler while I'm on the VPN due to this. Just thought I'll post a note for others who might be using this VPN client.
  9. Peter
    Peter avatar
    4 posts
    Member since:
    Sep 2015

    Posted 19 Sep 2015 Link to this post

    Just to add to this list: Hola.org also seems to be causing this.
  10. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 21 Sep 2015 Link to this post

    While disabling software that makes unwanted changes to your proxy setting is the best approach, some users may find the approach outlined here: http://www.telerik.com/forums/how-to-automatically-re-enable-fiddle-as-system-proxy sufficient.

    Regards,
    Eric Lawrence
    Telerik
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  11. Tony
    Tony avatar
    18 posts
    Member since:
    Sep 2014

    Posted 30 Sep 2015 in reply to Eric Lawrence Link to this post

    The link is broken and Google doesn't bring up the post when searching for those keywords
  12. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 30 Sep 2015 Link to this post

    Hello, Tony--

    The link is http://www.telerik.com/forums/how-to-automatically-re-enable-fiddle-as-system-proxy

    Regards,
    Eric Lawrence
    Telerik
    Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal and vote to affect the priority of the items
  13. Tony
    Tony avatar
    18 posts
    Member since:
    Sep 2014

    Posted 30 Sep 2015 in reply to Eric Lawrence Link to this post

     

    I too get the yellow bar several times a day. When I check the lan settings, I don't see a difference. All the checkboxes are always unchecked. Unless there's an app which changes it momentarily, I am not sure why Fiddler thinks the proxy settings have changed.

     

    Eric says if he enables auto re-enabling, a race condition or an infinite loop will happen. I am not sure if this would happen every time and if it does happen, then Fiddler can detect this scenario and display a message saying that it tried several times to reenable it within x period of time and it gave up and will stop trying to re-enable it.

    Anyways, I will try the re-enabling code mentioned in another post.

     

  14. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 01 Oct 2015 Link to this post

    Hi, Tony--

    > "All the checkboxes are always unchecked." 

    And that's a problem. While Fiddler is capturing, it sets the proxy settings to point to itself. If the proxy settings are cleared by other software, traffic will no longer flow to Fiddler.

    You can use Process Monitor to watch for writes to the ProxyServer registry key to see what software is whacking your proxy settings; typically this is caused by networking or VPN software.

    Regards,
    Eric Lawrence
    Telerik
    Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal and vote to affect the priority of the items
  15. Tony
    Tony avatar
    18 posts
    Member since:
    Sep 2014

    Posted 01 Oct 2015 in reply to Eric Lawrence Link to this post

    I ran Process Monitor and had two filters. One on path contains 'proxyserver' and one on operation contains 'set'. The attached capture shows all the changes are done to registry keys which belong to TrendMicro. I don't see keys belonging to the system's proxyserver. Yet these changes have triggered Fiddler's warning.

  16. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 02 Oct 2015 Link to this post

    Hi--

    It may well be the case that TrendMicro is the culprit here (insofar as they're known to attempt to run traffic through tmproxy.exe in order to "scan" it). 

    If you don't see writes to the ProxyServer key, try watching for writes to the ProxyEnable key instead.

    Regards,
    Eric Lawrence
    Telerik
    Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal and vote to affect the priority of the items
  17. John
    John avatar
    8 posts
    Member since:
    Aug 2015

    Posted 19 Feb Link to this post

    I downloaded Process Monitor, but I am getting overwhelmed with events. Over 1 million. How do I filter? Also, what am I looking for? My proxy gets changed instantly. When I click on the yellow bar, it instantly gets changed back. I know it's an IBM product doing it. I believe they calle it "zScaler" around here.
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