Posted by & filed under Developer Blog.

NOTE: This script is no longer supported in Flash Player 10.

(It was fun while it lasted!)

Let’s face it, there is such a thing as sensitive material on the web. I was recently put to the task of protecting a certain page on our company’s intranet from being redistributed outside the company. In other words, we have a page on the intranet that is so sensitive, upper managment doesn’t want our employees to be capable of sending it to anyone outside the company.

So, I started thinking, what are the ways an average, non-techie employee, could reproduce this information? Since it’s on our password/firewall protected intranet, the risk of someone just emailing the link isn’t an issue. Of course the obvious is that they could copy and paste the text into an email and send it that way. They could also press the Print Screen button and paste a snapshot of the page as an email attachment or whatever.

I decided that beyond more “advanced” measures (like view source then save as), the clipboard was the method most people know how to use. So, the question became “how to disable the clipboard?”

I started tinkering around with JavaScript solutions, attempting to intercept any ctrl+c or PrintScreen commands and over-ride them with a call to write a message to the clipboard: “You’re fired! Pack your things and go home.” which would in turn be pasted into their email if they attempted it. But this was klugy at best. First, JavaScript really needs a form field to have focus in order to fire an onClick type event. I figured the best way around that was to run as an onBlur and onFocus in the <body> tag and just over-ride the clipboard whether they tried to copy or not. This seemed to be a great solution until I realized that for some unknown reason, when you select text and then blur (remove focus) a browser window, it doesn’t actually fire any onBlur commands. Not only that, but it’s a big mess to add anything to the clipboard with Firefox (IE makes it really, really easy). I suppose that Firefox doesn’t make writing to the clipboard easy due to security issues, and I’m not going to complain about any attempt to make my favorite browser more secure.  😉

Then I remembered an Adobe Flash (that still sounds weird, doesn’t it?) application that I worked on a few years ago that used Flash’s built in clipboard functions. Booya! I cranked up Flash and wrote the following simple and very easy actionscript in the first line of the first frame:

this.onEnterFrame = function(){
System.setClipboard(“As long as this page is open your copy/paste functionality has been disabled.”);

(Added 08/28/2007: for the new CS3 use:)

addEventListener(Event.ENTER_FRAME, onEnterFrame);
function onEnterFrame(E){

System.setClipboard(“As long as this page is open your copy/paste functionality has been disabled.”);

I then set the movie size to 1px wide and 1px high and published. I then placed the Flash somewhere on the sensitive document.

Since I left my movie at the default 12 frames per second, the text “As long as this page is open your copy/paste functionality has been disabled.” will be set on the clipboard 12 times per second. Go ahead, try to beat that time with ctrl+c and then ctrl+v!

As invasive as this method is, it works. As long as that page is open even in the background, it will prevent any copying and pasting and even Print Screen and paste. The only problem is, that it requires Flash v6 or higher, which is required in my company to use many of our Flash based applications. But just in case, I left the following IE only code as a backup:

<body onBlur=’window.clipboardData.setData(“Text”, “As long as this page is open your copy/paste functionality has been disabled.”);’>