Very interesting, and evil: abusing the ETag mechanism for user tracking. (If a user requests some sort of unchanging resource without an etag, you give them a fresh one; and if they request a resource with an etag, you give it to them, with the supplied etag, and record the user.)
Even if Hulu turned off cookie respawning via etags, you can still track users this way, on the server side. I guess the tricky thing is to correlate the etag of the tracker resource with the rest of the requests that a user makes on a site.
> Even if Hulu turned off cookie respawning via etags, you can still track users this way, on the server side. I guess the tricky thing is to correlate the etag of the tracker resource with the rest of the requests that a user makes on a site.
The important distinction is that the ETag is literally no different than a cookie, when used this way. Turning off caching is the new turning off cookies.
> ...the tricky thing is to correlate the etag of the tracker resource with the rest of the requests that a user makes...
Not tricky though. Just put 1-pixel Etagged gif on every page. It gets requested on each page. Or just associate (server-side or client-side) the user's session cookie with the Etag.
Comments
Very interesting, and evil: abusing the ETag mechanism for user tracking. (If a user requests some sort of unchanging resource without an etag, you give them a fresh one; and if they request a resource with an etag, you give it to them, with the supplied etag, and record the user.)
Even if Hulu turned off cookie respawning via etags, you can still track users this way, on the server side. I guess the tricky thing is to correlate the etag of the tracker resource with the rest of the requests that a user makes on a site.
> Even if Hulu turned off cookie respawning via etags, you can still track users this way, on the server side. I guess the tricky thing is to correlate the etag of the tracker resource with the rest of the requests that a user makes on a site.
The important distinction is that the ETag is literally no different than a cookie, when used this way. Turning off caching is the new turning off cookies.
There is a difference: cookies get sent on requests to any resource in a domain, whereas etags get sent only to specific resources.
> ...the tricky thing is to correlate the etag of the tracker resource with the rest of the requests that a user makes...
Not tricky though. Just put 1-pixel Etagged gif on every page. It gets requested on each page. Or just associate (server-side or client-side) the user's session cookie with the Etag.