Saturday, December 30, 2006

How to Block Flash Cookies

Several web sites track you using a little known feature in Flash that lets them write files to your hard drive. These have been generally named "Flash Cookies". For example, I discovered that Amazon was using this. Even if you delete your browser's cookies (and cache and all else), they sometimes use the flash cookies to recognize you and flash your name in bold atop the Amazon web page. That's exactly what I don't want to see when surfing from an Internet cafe, or even from my own laptop sitting at Starbucks. Maybe I'm strange. I also don't wear my name on my shirt or hat.

Anyway, here's how to stop those flash cookies for people using Mac OS 10.3.9. I haven't yet examined this on my Windows XP system, and I don't yet own Tiger. The flash cookies are stored in 2 locations:

~/Library/Preferences/Macromedia/Flash Player/#SharedObjects/[some-strange-folder-name]
~/Library/Preferences/Macromedia/Flash Player/macromedia.com/support/flashplayer/sys

For a while I was routinely deleting the entire contents of these two folders. That has given me the confidence that this wasn't breaking anything. Lately, I went ahead and changed the permissions to these two directories using the simple "chmod -w" command from the shell. So far I haven't noticed any bad effects from this. So far all flash content still plays just fine.

2 comments:

Joe said...

Those folders are the same in Tiger (10.4.8).

I noticed cookies from flash based sites such as flickr and youtube.

Anonymous said...

For Windows it is
C:\Documents And Settings\%USERNAME%\ApplicationData\Macromedia\Flash Player\ followed by the path names mentioned within the post.