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With the release of the firesheep plug-in for firefox it has become trivial for website browsing on open Wi-Fi networks to be hijacked by 3rd party listeners.

Android offers the convenient auto-sync option. However I fear that my data may be auto-sync'd while I am connected to an open Wi-Fi network while at the local coffee shop or shopping mall.

Is all the data Android auto-syncs encrypted using SSL or a similar encryption mechanism? Is any auto-sync'd data unencrypted and transmitted in the clear for all to listen in to?

Update: COMPLETELY INSECURE!!!! See below!!!!

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German Heise Magazine has a great article about that question. It's just in german, but you could use an Translation Service. link:heise – NES Dec 14 '10 at 10:44
It seems, finally, Google will take care of its users data: – Eduardo May 26 '11 at 21:36
up vote 12 down vote accepted

Note: answering my own question as nobody knew.

I did a packet capture after selecting Menu -> Accounts & Sync -> Auto-sync (also accessible via the "Power Control" widget). What did I discover?

To my horror (http requests from phone displayed below):

GET /proxy/calendar/feeds/ HTTP/1.1
Accept-Encoding: gzip
Authorization: GoogleLogin auth=_hidden_
Connection: Keep-Alive
User-Agent: Android-GData-Calendar/1.4 (vision FRF91); gzip


GET /proxy/contacts/groups/ HTTP/1.1
Accept-Encoding: gzip
Authorization: GoogleLogin auth=_hidden_
GData-Version: 3.0
Connection: Keep-Alive
User-Agent: Android-GData-Contacts/1.3 (vision FRF91); gzip

My contacts and calendar are being transmitted unencrypted! I don't currently synchronize gmail so I couldn't say if that is unencrypted either.

Also the stock market application (which must be a service because I don't have the widget displayed or the application active):

POST /dgw?imei=TEST&apptype=finance&src=HTC01 HTTP/1.1
User-Agent: curl/7.19.0 (i586-pc-mingw32msvc) libcurl/7.19.0 zlib/1.2.3
Content-Type: text/xml
Content-Length: 338
Connection: Keep-Alive
Expect: 100-Continue

<?xml version="1.0" encoding="UTF-8"?>
<request devtype="HTC_Model" deployver="HTCFinanceWidget 0.1" app="HTCFinanceWidget" appver="0.1.0" api="finance" apiver="1.0.1" acknotification="0000">
<query id="0" timestamp="0" type="getquotes">

Completely unencrypted request for stock quotes: just think, you could sit in Starbucks in the financial centre of your city and packet-sniff what quotes were important to all the smart phone users around you..

Other items that were not encrypted:

  • http request to
  • time request to (doesn't even use NTP)

About the only data that is encrypted on my phone are the mail accounts I set up with the K-9 application (because all my mail accounts use SSL - and fortunately gmail accounts are, by default, SSL; and yahoo! mail supports imap using SSL too). But it seems none of the auto-sync'd data from the out-of-box phone is encrypted.

This is on a HTC Desire Z with Froyo 2.2 installed. Lesson: do not use phone on open wireless network without VPN encrypted tunnelling!!!

Note, packet capture taken by using tshark on ppp0 interface on virtual node running Debian connected to Android phone via OpenSwan (IPSEC) xl2tpd (L2TP).

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That's worrying. I can't see any cookies passing back and forward there, are they being sent in the clear too? – GAThrawn Dec 1 '10 at 9:47
The auth= string contained what appeared to be similar to a cookie, I deleted it before posting here for security, however. – PP. Dec 1 '10 at 9:53
Is this still a current problem on Android 2.3.1? – meinzlein Nov 25 '11 at 18:13
I believe you can set up Android 4 to always use a VPN connection. – intuited Nov 25 '13 at 18:12

Results captured on an LG Optimus V (VM670), Android 2.2.1, stock, rooted, purchased in March 2011.

As of today, the only unencrypted requests I could find in a pcap taken during a complete resync were:

Picasa Web Albums

GET /data/feed/api/user/<username>?imgmax=1024&max-results=1000&thumbsize=144u,1024u
    &visibility=visible&kind=album HTTP/1.1
GData-Version: 2
Accept-Encoding: gzip
Authorization: GoogleLogin auth=<snipped>
If-None-Match: <snipped; don't know if it's sensitive info>
Connection: Keep-Alive
User-Agent: Cooliris-GData/1.0; gzip

That's it.

Picasa was the only service I could find being synced unencrypted. Facebook requested a couple profile images (but didn't pass any account info); Skype requested ads; and TooYoou grabbed a new banner image. None of those relate to sync, really.

So it looks like Google's syncing security has been tightened quite a bit. Turn off syncing Picasa Web Albums and all of your Google data should be synced in encrypted form.


This bothered me a little:

GET /market/download/Download?userId=<snipped>&deviceId=<snipped>
    &downloadId=-4466427529916183822&assetId=2535581388071814327 HTTP/1.1
Cookie: MarketDA=<snipped>
Connection: Keep-Alive
User-Agent: AndroidDownloadManager

The return of this is a 302 Moved Temporarily that points to a highly complex download URL:

HTTP/1.1 302 Moved Temporarily
Cache-control: no-cache
Pragma: no-cache
Content-Type: text/html; charset=UTF-8
Date: Fri, 25 Nov 2011 08:37:09 GMT
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
Server: GSE
Transfer-Encoding: chunked

Android's download manager turns right around and requests that download location, passing the MarketDA cookie again.

I don't know if there's any security danger from how Market downloads APKs. The worst I can imagine is that unencrypted APK downloads open up the possibility of interception & replacement with a malicious package, but I'm sure Android has signature checks to prevent that.

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I'm glad that since my initial discovery that others are taking this seriously now. Thank you! I felt I was alone in the wilderness when I posted the initial question/response. I've not actually done any retesting since the original post and kept to more secure practices - but I'm glad that others are following up on this. – PP. Dec 19 '11 at 12:20
I get funny looks from people sometimes because I spout off about security like it's normal. And three days after posting this, I snapped up a Cyber Monday deal on a new Motorola Triumph. Customer service issues delayed its arrival until last Wednesday, but I quickly discovered that it has major issues with EAP-secured networks. My college uses EAP. So I'm glad I looked into this. More may be coming, as I haven't yet tested Currents. ;) – dgw Dec 20 '11 at 10:10
I only want to encourage you - sound like a good person to care enough about security. – PP. Dec 22 '11 at 14:25

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