Google knows nearly every Wi-Fi password in the world

If an Android device (phone or tablet) has ever logged on to a particular Wi-Fi network, then Google probably knows the Wi-Fi password. Considering how many Android devices there are, it is likely that Google can access most Wi-Fi passwords worldwide.

Recently IDC reported that 187 million Android phones were shipped in the second quarter of this year. That multiplies out to 748 million phones in 2013, a figure that does not include Android tablets.

Many (probably most) of these Android phones and tablets are phoning home to Google, backing up Wi-Fi passwords along with other assorted settings. And, although they have never said so directly, it is obvious that Google can read the passwords.

Sounds like a James Bond movie.

Android devices have defaulted to coughing up Wi-Fi passwords since version 2.2. And, since the feature is presented as a good thing, most people wouldn't change it. I suspect that many Android users have never even seen the configuration option controlling this. After all, there are dozens and dozens of system settings to configure.

And, anyone who does run across the setting can not hope to understand the privacy implication. I certainly did not.


  • In Android 2.3.4, go to Settings, then Privacy. On an HTC device, the option that gives Google your Wi-Fi password is "Back up my settings". On a Samsung device, the option is called "Back up my data". The only description is "Back up current settings and application data". No mention is made of Wi-Fi passwords.
  • In Android 4.2, go to Settings, then "Backup and reset". The option is called "Back up my data". The description says "Back up application data, Wi-Fi passwords, and other settings to Google servers".

Needless to say "settings" and "application data" are vague terms. A longer explanation of this backup feature in Android 2.3.4 can be found in the Users Guide on page 374:

Check to back up some of your personal data to Google servers, with your Google Account. If you replace your phone, you can restore the data you’ve backed up, the first time you sign in with your Google Account. If you check this option, a wide variety of you personal data is backed up, including your Wi-Fi passwords, Browser bookmarks, a list of the applications you’ve installed, the words you’ve added to the dictionary used by the onscreen keyboard, and most of the settings that you configure with the Settings application. Some third-party applications may also take advantage of this feature, so you can restore your data if you reinstall an application. If you uncheck this option, you stop backing up your data to your account, and any existing backups are deleted from Google servers.

A longer explanation for Android 4.0 can be found on page 97 of the Galaxy Nexus phone users Guide:

If you check this option, a wide variety of your personal data is backed up automatically, including your Wi-Fi passwords, Browser bookmarks, a list of the apps you've installed from the Market app, the words you've added to the dictionary used by the onscreen keyboard, and most of your customized settings. Some third-party apps may also take advantage of this feature, so you can restore your data if you reinstall an app. If you uncheck this option, your data stops getting backed up, and any existing backups are deleted from Google servers.

Sounds great. Backing up your data/settings makes moving to a new Android device much easier. It lets Google configure your new Android device very much like your old one.

What is not said, is that Google can read the Wi-Fi passwords.

And, if you are reading this and thinking about one Wi-Fi network, be aware that Android devices remember the passwords to every Wi-Fi network they have logged on to. The Register writes

The list of Wi-Fi networks and passwords stored on a device is likely to extend far beyond a user's home, and include hotels, shops, libraries, friends' houses, offices and all manner of other places. Adding this information to the extensive maps of Wi-Fi access points built up over years by Google and others, and suddenly fandroids face a greater risk to their privacy if this data is scrutinised by outside agents.

The good news is that Android owners can opt out just by turning off the checkbox.

Update: Sept 15, 2013: Even if Google deletes every copy of your backed up data, they may already have been compelled to share it with others. And, Google will continue to have a copy of the password until every Android device that has ever connected to the network turns off the backing up of settings/data.

The bad news is that, like any American company, Google can be compelled by agencies of the U.S. government to silently spill the beans.

When it comes to Wi-Fi, the NSA, CIA and FBI may not need hackers and cryptographers. They may not need to exploit WPS or UPnP. If Android devices are offering up your secrets, WPA2 encryption and a long random password offer no protection.

I doubt that Google wants to rat out their own customers. They may simply have no choice. What large public American company would? Just yesterday, Marissa Mayer, the CEO of Yahoo, said executives faced jail if they revealed government secrets. Lavabit felt there was a choice, but it was a single person operation.

This is not to pick on Google exclusively. After all, Dropbox can read the files you store with them. So too, can Microsoft read files stored in SkyDrive. And, although the Washington Post reported back in April that Apple’s iMessage encryption foils law enforcement, cryptographer Matthew Green did a simple experiment that showed that Apple can read your iMessages.

In fact, Green's experiment is pretty much the same one that shows that Google can read Wi-Fi passwords. He describes it:

First, lose your iPhone. Now change your password using Apple's iForgot service ... Now go to an Apple store and shell out a fortune buying a new phone. If you can recover your recent iMessages onto a new iPhone -- as I was able to do in an Apple store this afternoon -- then Apple isn't protecting your iMessages with your password or with a device key. Too bad.

Similarly, a brand new Android device can connect to Wi-Fi hotspots it is seeing for the very first time.

Back in June 2011, writing for TechRepublic, Donovan Colbert described stumbling across this on a new ASUS Eee PC Transformer tablet:

I purchased the machine late last night after work. I brought it home, set it up to charge overnight, and went to bed. This morning when I woke I put it in my bag and brought it to the office with me. I set up my Google account on the device, and then realized I had no network connection ... I pulled out my Virgin Mobile Mi-Fi 2200 personal hotspot and turned it on. I searched around Honeycomb looking for the control panel to select the hotspot and enter the encryption key. To my surprise, I found that the Eee Pad had already found the Virgin hotspot, and successfully attached to it ... As I looked further into this puzzling situation, I noticed that not only was my Virgin Hotspot discovered and attached, but a list of other hotspots ... were also listed in the Eee Pad's hotspot list. The only conclusion that one can draw from this is obvious - Google is storing not only a list of what hotspots you have visited, but any private encryption keys necessary to connect to those hotspots ...

By Michael Horowitz
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