Galaxy S3 keeps switching wifi settings to use a manual proxy I get no internet connection message.  I go to wifi settings, and something has changed it to use a manual proxy setting.  I don't have a proxy server.  it's a home network.  I switch it to no proxy, save, and all is good for about a minute, maybe less.  I look at network settings, and boom, it's using a manual proxy again.  How do I stop this?
There's either an app that's controlling this setting, or malware. On Windows behavior like this is caused by malware 9 out of 10 times, but on Android I'd suspect that some app is the likely culprit.

For a list of apps with permissions to monkey around with your settings, go to Settings&rarr;Security&rarr;Device Administrators. Anything listed there that has a checked box on the right has permissions to control settings on your device. See if there is anything in the list that stands out, such as security software or network-related software. Try to isolate which one is the culprit by unchecking the enabled device administrators one at a time and then checking whether changes you make to the proxy settings stick.

I did a quick search on this and I'm seeing that Kaspersky Mobile Security comes up frequently as an app that makes changes to the WiFi proxy settings revert to "Manual" with a localhost IP address (127.0.0.1). Is that the IP address you're seeing, and do you have Kaspersky Mobile Security installed?

According to this thread in the Kaspersky support forums, there was a known bug related to this issue in version 10.4.45. A Kaspersky rep said it would be fixed in the next version in June 2013, but according to this thread in the Vodafone forums there was still an issue with this in a later version:


  Thanks for your suggestions guys, I think I have solved this one.  I found other people were having the same issue who were using Kaspersky Mobile Security.  I've just uninstalled it  (version 10.4.47) and not only has this issue completely gone, another weird issue I was having where the WiFi connection took 3 - 4 attempts before it settled on a connection has also gone. Happy bunny.  
  
  I need an internet security app though so I may try that Lookout app you mentioned.


I'm not familiar with Kaspersky Mobile Security, so I can't tell you whether that means that the behavior of changing proxy settings is itself a bug that has not been fixed, or that there used to be a more specific bug with this feature but the behavior in general is part of the functionality of the app. However, I can tell you that I've been using Lookout for about a year and haven't had this or any other problem with it.