All entries for Sunday 24 January 2010

Flash Cookies

Flash as in the ubiquitous Flash Player from Adobe rather than someone who can save every one of us.

Cookies as in the things website use to keep track of you rather than delicious sugar and preferably chocolate based snacks which in this country we call biscuits.

The other day I learnt that Flash can use cookies. Not cookies that show up when you tell your web browser to show you a list of cookies it has stored, but cookies which it stores independently of the web browser. It's one of those things I read about and think 'how did I not know about this?'. I became aware of it from a from a comment on a Slashdot article (I forget which one) then looked for more info found this Wired article which helpfully tells you where the cookies are stored on various operating systems. So take a look, if you feel so inclined. I found loads of cookies. Which I then deleted.

I initially thought it was a little sneaky keeping the cookies in a directory called macromedia given that Flash is an Adobe product, but I guess it's a legacy thing left over from when the days before Macromedia was consumed by Adobe. So it's backwards compatibility rather than sneakiness. It is rather irritating, and just a bit odd, that they decided to call the directory #SharedObjects though. Yes, that's a filename that starts with a #. (*nix minded people know what I'm getting at.)

The comment on Slashdot recommended removing the write permission from the #SharedObjects as a way of preventing Flash from writing cookies. Out of curiosity I gave it a go. Unsurprisingly, it does indeed stop Flash writing cookies. However I quickly discovered a downside to doing this when I started watching something on iPlayer. About ten seconds in to the programme the picture froze and shortly after Flash popped up the message  "A script in this movie is causing Adobe Flash Player 10 to run slowly. If it continues to run, your computer may become unresponsive. Do you want to abort the script?" I clicked yes and the programme continued to play but the timeline indicator didn't work. After I pressed stop it didn't know where to restart from when I hit play again. So remove the write permission clearly isn't a sensible thing to do unless one doesn't mind such breakage on some websites.

What's most interesting is that sites where you haven't consciously used Flash, such as iPlayer, are also setting cookies using Flash. After deleting all my Flash cookies and taking a look in the directory the next day to see what was there I found one from ia.media-imdb.com. I'd visited imdb since deleting the cookies, but nothing I interacted there used Flash. I might give Flashblock a go.

Mike Willis : 24 Jan 2010 17:08 |  Comments (0) |  Close comments |  Report a problem