One could request that Sophos add this to the web filter under advertising or whatever.
Re disabling JavaScript: I use 'NoScript' in my browsers, which can block (blacklist or whitelist) individual sites. Blocking addthis.com/.net should do it.
Also, I don't understand why the article says that AdBlock+ wouldn't be able to block it.
As far as I understood that technique (little googling delivers lot of informations to that matter), I would assume, that a specific recognition of Canvas Fingerprinting may be a difficult matter or even impossible to completely detect and handle on a gateway, as it seems to use legitimate html5 techniques in a "creative way" to fingerprint a system unigue behaivour by rendering hidden graphics or texts.
At least my in this thread explained approach to block advertisers and trackers may help in todays situation, as AddThis seems to be the inventor of that technique (and also the mainly used one in most tested websites according to many resources in the www), and it's listed and possible to block with that guide as adverstiser or tracker in the application control. So my (unproven) theory is, that blocking AddThis also should block their fingerprinting (If you can't block the packet, block at least the bad guy trying to deliver it...).
But if some sites start to deliver this techniques/scripts from directly their own domain instead embedded external tracker scripts, we users in general may get a hard time to fight them. At least there seems to be first browser addons (and in-browser techniques to avoid such bad stuff) in development to defend against it in general. If this will become a real issue/concern in the future, and blocking the nosy guys delivering it will not help anymore, I hope too that Sophos maybe will figure out some techniques for their products to protect against canvas fingerprinting (as there are sitting a lot of smart devs and researchers around which also figured out lot of other stuff in the past )
