Wednesday, January 4, 2012

Android Security with the bookmark_thumb1 directory

My wife has been going through a LOT of hoops with T-Mobile and the piece of trash Sidekick phone that I bought for her. Through all of this, she asked me to look at her microSD card to make sure that there wasn't anything malicious on there.

I had no problem with doing this and it even gave me an excuse to go through six other microSD cards that I haven't looked at in a long time (and it was GOOD that I DID finally look....but that is a whole different subject). So I logged into my box and plugged the microSD card into an adapter and then into the computer. I have looked at almost every file that exists on a microSD used by an Android phone (2.2.1 and earlier) so nothing really stuck out in the file directories. However, one thing DID stick out.

Android uses a folder called .bookmark_thumb1 under the root. I have never been suprised by this folder until the night I was doing this check for my wife, and thus I have NEVER made the time to actually look into the purpose of the folder. Suffice to say that when I glanced at the screenshots that were in this folder, I was very (VERY) annoyed to see the login page for one of my banks as well as all of the login boxes filled in. Now, these were just screenshots, so there was no revelation of the password used even though the username was definitely visible. This caused me to want to look into this folder a little bit.

After getting back to the hotel tonight and still being wired from Michigan's win over Virginia Tech, I thought I would spend five minutes on this. What I have learned:
- The behaviour (taking screenshots of ANY page you visit) is common and actually used by the system in relation to the bookmark maintaining.
- This is not, but "could" be a security risk
- There is both a permenant fix and a temporary fix.

What follows are just a couple steps for the permenant and temporary fixes and some links to some articles already published about this folder.

Temp Fix
After you are done browsing the web (and maybe using some applications), us a file brower (either from the market place or via mounting the SD/microSD card to your laptop) and delete the files or the whole folder. The folder is automatically recreated when a new internet browsing session is initiated.

Permenant Fix
Delete the .bookmark_thumb1 folder. create a blank textfile with the name  .bookmark_thumb1.  The bookmarking implementation will no longer work properly, but the folder will NOT be recreated and there will be NO more storage of session bookmarks.


So this isn't a "new" issue...probably isn't an issue to most people. BUT, I did spend a few minutes researching it so it was worth mentioning on here.