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I recently had a phone stolen. It's been replaced, I've changed my passwords, the phone company has shut down connectivity for the stolen one... I think I'm pretty much as safe as I can be.

However, it did get me wondering. How secure is the pattern lock? My phone had a pattern lock, so I assume that means that the casual user can't pick it up and do anything.

But if one had all the time in the world and some technical know-how, could they circumvent it?

Or is the phone only useable if the person wipes it and starts over?

Note 1: I know the data on the SD card is a separate issue, I'm just wondering about the phone and it's internally stored data.

Note 2: I've seen other questions about recovery of the password via one's Google account, but the person who has taken my phone (presumeably) doesn't have the ability to reset my pattern that way, so I believe this question is a separate issue.

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    As it has been said before, when your hardware falls into the wrong hands, all bets are off -- there's virtually no protection against a sufficiently skilled and motivated hacker.
    – Martin Tapankov
    Commented Jan 26, 2012 at 9:02
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    Without listing exactly how valuable the contents of your phone are, such question is impossible to answer. When you ask "How secure?", do you mean: "how secure" for your kid, for your neighbour, for a professional programmer, for an Android guru or for an intelligence agency? General questions call for general answers.
    – Martin Tapankov
    Commented Jan 26, 2012 at 14:37
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    @MartinTapankov: Right. Thus: Generally speaking, fearing the absolute extremes of possibility is unrealistic and unneccessary. Do I really have to specify that I'm not an international spy in order to get a straight answer?
    – Questioner
    Commented Jan 26, 2012 at 15:10
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    Generally speaking, unless the person stole your phone with specific intentions of getting at your data then they probably don't care about it. Even if they knew how to circumvent it. Typically they are more interested in the hardware. Of course if they do circumvent it and take a look and spot something really tempting, then you may be in trouble.
    – Jim McKeeth
    Commented Jan 30, 2012 at 21:36

4 Answers 4

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You don't even need much technical know how to crack most touch screen phones. There was a white-paper written recently about the security of touch screen lock mechanisms (and pattern locks in particular) and breaking into these devices using purely the greasy smudges on the screen to get the unlock code.

8 Conclusion
In this paper we explored smudge attacks using residual oils on touch screen devices. We investigated the feasibility of capturing such smudges, focusing on its effect on the password pattern of Android smartphones. Using photographs taken under a variety of lighting and camera positions, we showed that in many situations full or partial pattern recovery is possible, even with smudge “noise” from simulated application usage or distortion caused by incidental clothing contact. We have also outlined how an attacker could use the information gained from a smudge attack to improve the likelihood of guessing a user’s patterns. ...

Smudge Attacks on Smartphone Touch Screens (PDF)

The rest of the paper is well worth a read too.

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  • Thats what I mentioned above, but I cant find the paper at this time.
    – Leandros
    Commented Jan 26, 2012 at 13:55
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    @DaveMG I think the "Variety of lighting and camera positions" were actually just so that they could simulate in a repeatable way how you'd hold the phone up to the sun and change its angle until all of the smudges are clear. That said they also did a bit of contrast changes and colour enhance on some of the photos to make things easier to see in some cases (Figure A6 is a good example). Personally I think, whilst unlikely, this sort of thing is far more likely than a casual thief using the ADB debug tools to inspect the phone's internal memory.
    – GAThrawn
    Commented Jan 26, 2012 at 14:04
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    @DaveMG Have a look at this piece of work about getting PINs off an ATm using IR: nakedsecurity.sophos.com/2011/08/17/…
    – Peanut
    Commented May 1, 2012 at 16:41
  • @GAThrawn Relating to the paper you posted if you read it they don't really use that realistic an attack scenario "We based our usage simulation on the telephone application;" If you look at the picture they didn't really use it much in terms of swiping up and down for a start and for myself at least the telephone app is actually one of the least used.
    – Peanut
    Commented May 1, 2012 at 16:48
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It is insecure depending on a few cases*.

Here's a sample of an exploit that a hacker or an above average user can do (with the adb tool and the phone connected to a PC) :-

Code to crack pattern lock Exploit 2

******May only apply on rooted devices. (not all adb commands require root though) "USB debugging" should also be set prior to using the adb tool*. But as eldarerathis said, some devices can also be rooted through the ADB. In fact, a skilled hacker may also find loopholes for gaining access to the internal data. (perhaps even find a way to utilize the adb without the usb debugging option)

The Android Pattern lock also has many glitches making it relatively unsecure. Here's an example..

While the exploits mentioned above and certain glitches may be fixed by Google in the upcoming versions, a pattern lock remains a pattern lock. ie, It can be considered as a mere solid gateway to using the android's user interface. A pattern lock does not encrypt the contents of a phone. It will not stop a hacker from playing around using the adb shell. He can view the internal memory of the phone etc using the adb tool which is freely provided in the Android SDK

Also, the internal memory is pretty much compromised as there may be other ways to mount it or read it.

All I can say for now is it would be better if you disable "usb debugging" unless you need it, as an added security measure.

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    I don't understand where the hacker would input this. Wouldn't they need to gain access by USB, and to do that, wouldn't they need to grant access from the device? Or is this executed by some kind of recovery boot or something?
    – Questioner
    Commented Jan 26, 2012 at 10:53
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    This work only, if the phone is rooted. (Just want to say)
    – Leandros
    Commented Jan 26, 2012 at 12:58
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    @Dave: This also won't work if USB debugging is disabled, since the lock would prevent you from accessing the setting to turn it on. Given a rooted and debugging-enabled phone, though, this does work (and in your case it sounds like this does not apply).
    – eldarerathis
    Commented Jan 26, 2012 at 14:19
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    @DaveMG: Theoretically, an attacker could attempt to root your device via adb if debugging was turned on, then. Whether or not they succeeded would depend on the specific device and Android version, I suppose, since some have easily exploitable vulnerabilities (like Gingerbreak) and others do not.
    – eldarerathis
    Commented Jan 26, 2012 at 15:16
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    This method don't work! The row lock_pattern_autolock doesnt exists. Just my 2 cents
    – Leandros
    Commented Jan 28, 2012 at 17:49
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At least on most phones you can just hold down the volume key/keys to get to the fastboot/recovery. From there one can easily get adb connection, even if you don't have usb debugging on, and access straight to the internal memory. From there it is even possible to root the phone to make it possible to edit internal files and disable the lock, like Power-Inside suggested. All this can be done in several minutes!

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  • By holding down the volume key/keys while booting, you can get to fastboot/recovery, like I said. I believe that this gives you instant adb access. You can even root (at least most phones) from there
    – varesa
    Commented Feb 1, 2012 at 13:05
  • Phones do it slightly differently. On galaxy 2 you seem to have to hold volume down and home.
    – varesa
    Commented Feb 2, 2012 at 5:54
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The pattern is not very safe, because you can simply do a data wipe in recovery. And you're in the phone. In addition the pattern can often seen in the screen, because you swipe everytime you unlock your phone this pattern.

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    recovery and format are always accessible afaik, but the poster is more concerned about his internal data being accessible "..I'm just wondering about the phone and it's internally stored data."
    – Irfan
    Commented Jan 29, 2012 at 6:48

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