Norton Image Blocking
We had a call from a client the other day regarding the e-commerce site we’re developing for them. They had a query about the page that shows all the top levels of product categories, and the conversation went something like this —
Client: Are you going to put product thumbnails for each of the main categories on that top-level page?
Us: Er, yes, we did about two weeks ago…
Client: Well I can’t see them….
[We quickly fire up IE to check]
Us: They’re definitely there….
The client sent us a screenshot, and sure enough, no images. So after making sure it wasn’t a caching issue, we asked them to view source on the page. Instead of having a couple of dozen divs, each containing a heading and a thumbnail image, all they were getting were the divs and headings, with no sign of the HTML for the images. Weird.
Clearly something was blocking out those thumbnails at their end, but leaving all the other images in place. When we asked about their firewall, they told us they were using Norton Internet Security. It was the only possible explanation, but why was it filtering out those particular images? Neither the image markup nor the URLs they were linking to contained any suspicious words (e.g. banner, ad, cgi, popup etc.) or any javascript/Active X, and the thumbnails were all being loaded from a directory on the same server. What could it possibly object to?
After a quick Google I discovered the answer: Norton thought they were adverts, and blocked them automatically. Now being one of the largest security software companies, you’d think that Symantec/Norton would have developed some complex algorithm for recognising adverts. But no, this sophisticated software blocked images based purely on their dimensions. Because our product thumbnails were 180px high by 150px wide, Norton removed them from the markup altogether, without alerting the user that it had done so.
It turns out that with ad-blocking turned on (the default setting), Norton will block any images that match some dimensions commonly used by adverts. The blacklisted dimensions seem to be:
- 120 x 240
- 120 x 90
- 468 x 60
- 234 x 60
- 120 x 60
- 125 x 125
- 180 x 150
In the end I had two options to get round Norton’s idiocy — resize the existing thumbnails by a pixel or two and modify the CMS so that any images added by the client would be OK, or change the way the CMS output the HTML for the thumbnails. I opted for the latter:
<img src="foo.jpg" alt="bar" height="180" width="150" />became:
<img src="foo.jpg" alt="bar" style="height: 180px width: 150px" />Not particularly elegant, but as soon as I did it, the client was able to see the images again.
I don’t have anything against people blocking adverts (I’ve done so myself using the hosts file), but really I think it should be done at the request of the users, on a per-domain basis. If a piece of software is going to blanket ban any image that it thinks is an advert, then surely it should make that decision based on something more concrete than the its dimensions. I wouldn’t trust any program that stupid to look after my security.
Norton Internet Security quick capsule review: piece of shit.
Wow, I’m glad I found this article… I’ve been having the same exact problems on my forum. I had multiple users who were saying they couldn’t see the banners… yet I could. Reading your post was like deja vu… I had one guy send me a screenshot, then the page source… and yeah, deja vu. I didn’t think my banners were at am ‘advertising’ resolution (675×225)…? Or do you think they were blocked because they were in a “banners” directory? Then they reported that when they turned Norton off, the banners worked… which led to the Google search which sent me here.
Long story short, thanks for posting this. ;]
Norton won’t like the word “banners” being in the URL of the image either. In addition to blocking images of certain dimensions, it has a long, long list of keywords that trigger the blocking too. You can find a partial list here - basically you have to avoid anything that sounds remotely like an ad-related term. Hope this was of some use - and that it doesn’t create too much extra work for you!
I had the same problem on my website. One of my customers could not see some links in their admin panel. They just were not showing up. I racked my brain and could not see what why it was so.
Because logic that shows the links in their admin panel is so variable (e.g shown according to what products they have, whether they have ever spent money, if they need to renew subscriptions etc) I spent a good few hours checking the logic of the code trying to find the bug.
The customer even mentioned they had Norton running and suggested it was adblocking software causing it - I, stupidly, said “No, it can’t be that, because the links are not ads!”. How wrong was I!
;o)
I ended up driving 100 miles to their house and sat down at their computer to see how it looked from their point of view. Sure enough Norton’s AntiNet software was blocking the links because it they contained a key/value pair with the word ‘ad’ in it.
Now if a customer complains that something is not working, the first thing i do i send them to do the ‘Circle Test - Test Your PC for Ad Blocking Software’, to find out if they have problems.
Here’s the one i use:
http://www.startinbusiness.co.uk/spot_diff/spot_the_difference.htm
Thanks Terri, that’s a handy link - definitely worth bookmarking.
Thanks again for this post. Had the same problem, but Norton seamed to be blocking images on pages only because they were of dimensions 250px by 250px. These dimensions were not on the list given above. Wander how many other image sizes are on it’s “black list”!