LinuxQuestions.org
Welcome to the most active Linux Forum on the web.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Software
User Name
Password
Linux - Software This forum is for Software issues.
Having a problem installing a new program? Want to know which application is best for the job? Post your question in this forum.

Notices


Reply
  Search this Thread
Old 09-07-2013, 03:51 PM   #1
Z038
Member
 
Registered: Jan 2006
Distribution: Slackware
Posts: 855

Rep: Reputation: 169Reputation: 169
firefox privacy concern over new tab screen capture thumbnails


This is not a new Firefox privacy concern, but I just found out about it. It's existed since about FF12 or so. I wanted to mention it to raise awareness. If you care about your browsing privacy, you may want to take note.

What all Firefox users know is that when you open a new browser tab, FF displays a page with nine screen shots randomly chosen from among your most visited sites. You can toggle the display of the images by clicking a small grey grid icon in the upper right hand corner of the screen. I didn't like the idea that someone looking over my shoulder could see screen shots of the web sites I've visited, so I turned off the new tab display when FF first introduced it.

What many FF users may not be aware of is that toggling off the display does not stop the screen images from being captured and stored in your cache. A new image is captured of the page you are presently viewing whenever you launch a new tab, regardless of whether you've turned off the new tab view.

You can find the images in your home folder under .cache/mozilla/firefox/<yourdefaultfolder>/thumbnails/. I'm not sure what controls the number of png files that are stored there. On my system, there weren't that many, perhaps a couple dozen, but I tend to clear my Firefox browsing history and cache on a fairly routine basis.

Some people may not care that screen shot thumbnails of sites they visit are being recorded and stored by Firefox. In fact, many people may find it useful. But at one time, FF was capturing screen images of https sites, which might include things like your bank login screen. Probably no one would like that. I read somewhere that FF has stopped capturing screen images of secure web sites, but I didn't bother to test it myself to verify. I just wanted to turn off the screen captures entirely.

There is an option you can add to about:config to stop Firefox from capturing screen images for the new tabs page. It doesn't exist by default, so you have to add it. Go to about:config, create a new boolean value called "browser.pagethumbnails.capturing_disabled", and set it to true. I had to restart FF to make it take effect. I've been monitoring for a day, and I haven't seen any new screen shots being saved since I set that option. Remember to delete or shred any existing png files in your firefox thumbnail cache.

What brought all this to my attention was my accidental deletion (via shift+delete) of a folder of important files a couple of days ago. I used photorec to scan the file system for deleted files so I could recover them. Photorec found 50,000 deleted files in total, and among those were roughly 8,900 deleted png files. Of those, I estimate 90% or more were Firefox web site screen shots going back many months, forming a visual history of my browsing activity over that time.

For more complete info, search the web for Firefox new tab thumbnails privacy or similar, and you'll find plenty.
 
Old 09-08-2013, 09:43 AM   #2
H_TeXMeX_H
LQ Guru
 
Registered: Oct 2005
Location: $RANDOM
Distribution: slackware64
Posts: 12,928
Blog Entries: 2

Rep: Reputation: 1292Reputation: 1292Reputation: 1292Reputation: 1292Reputation: 1292Reputation: 1292Reputation: 1292Reputation: 1292Reputation: 1292
I think this option may do the same thing, because I don't have any thumbnails:
Code:
nglayout.enable_drag_images false
You can try it and see.
 
Old 09-08-2013, 09:45 AM   #3
jdkaye
LQ Guru
 
Registered: Dec 2008
Location: Westgate-on-Sea, Kent, UK
Distribution: Debian Testing Amd64
Posts: 5,465

Rep: Reputation: Disabled
Thank you Z038. That is both interesting and useful.
Well done.
jdk
 
Old 09-08-2013, 10:17 AM   #4
Z038
Member
 
Registered: Jan 2006
Distribution: Slackware
Posts: 855

Original Poster
Rep: Reputation: 169Reputation: 169
Quote:
Originally Posted by H_TeXMeX_H View Post
I think this option may do the same thing, because I don't have any thumbnails:
Code:
nglayout.enable_drag_images false
You can try it and see.
I tried it. It doesn't appear to be related to the full screen image captures that FF displays on a new tab page when the image grid icon in the upper right corner of a blank tab page is toggled on. Whether nglayout.enable_drag_images is toggled on or off, no thumbnail images get written to the thumbnail cache.

What nglayout.enable_drag_images does is control the "drag feedback" image. The description says "Use to eliminate/remove/hide/restore ghost image/picture attached to cursor when dragging link, favicon, picture, or tab."

What I observe is that if it is set to true, a copy of the object being dragged on the UI will be attached to the cursor while dragging. If set to false, a generic icon appears instead of a copy of the object. The difference is seen easily on any LQ page by toggling the setting on or off, and then dragging a link, or the group of four Tux's that appear in the upper left corner of the screen, or an icon, etc.

Most of the objects that can be dragged are already discrete elements of the page, such as a gif, png, or jpg, so perhaps FF doesn't have to make a thumbnail of them. A copy of a link being dragged may be a different story. I don't have a clue how a GUI or windowing system works. If there is a cache of dragged objects or images of them being stored somewhere, it could also have privacy implications, but if such a thing exists, it doesn't appear to be in the thumbnail cache.
 
Old 09-08-2013, 10:26 AM   #5
Z038
Member
 
Registered: Jan 2006
Distribution: Slackware
Posts: 855

Original Poster
Rep: Reputation: 169Reputation: 169
Quote:
Originally Posted by jdkaye View Post
Thank you Z038. That is both interesting and useful.
Well done.
jdk
You're welcome jdk. I would probably never have noticed the cache of screen images if I hadn't run photorec to find deleted files in the free space of my drive. It makes me wonder how space is allocated and reused in an ext4 file system. That photorec was able to recover over 8,000 of these png images created by FF going back at least a year was quite surprising to me, given how much churn I have in the file system mounted on /home.
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
Running Xvidcap (for screen capture ) + audacity (for audio capture) simultaneously vikram_cvk Linux - Software 2 05-20-2011 04:26 AM
Concern regarding latest firefox update sorbyl Linux - Newbie 2 03-06-2009 07:19 AM
How to capture thumbnails from a movie fw12 Linux - General 1 12-11-2007 12:36 PM
Fluxbox - Problem with Alt-Tab and Firefox Full Screen windz Linux - Desktop 2 04-17-2007 05:52 AM
Deleting thumbnails from /root/thumbnails directory moxieman99 Linux - Newbie 3 10-19-2004 04:45 PM

LinuxQuestions.org > Forums > Linux Forums > Linux - Software

All times are GMT -5. The time now is 12:44 AM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration