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Imagine that every time you print a document, it automatically includes a secret code that could be used to identify the printer -- and, potentially, the person who used it. Sounds like something from a spy movie, right?

Unfortunately, the scenario isn't fictional. Most color laser printers and color copiers are designed to print invisible tracking codes across every single printed page of their output. These codes reveal which machine produced a document and, in some cases, when the document was printed or copied.

In this instructable, we'll describe three different ways to see the tracking dots your printer produces: with a blue light, with a microscope, or with a scanner. If you don't have the necessary equipment for a particular step, go on to the next one.

For further information, or to share your findings, please visit us at http://www.eff.org/issues/printers.

Want to help? Download test sheets at http://www.eff.org/wp/investigating-machine-identification-code-technology-color-laser-printers#help

Step 1: Print a page with text/graphics


Print out a page from a color laser printer. The page should use color and have some text or graphics on it. You can find a list of printers that we know print tracking dots at our website.

As you're looking for the dots, keep in mind that they're printed in a regularly repeating pattern across the entire page (not just in the corner of the page), and will be intermixed with other printed data.

What about B/W laser printers.
<p>I saw on a CSI-like program they said printers put a unique code on the sheet, the prop that they used (from a B&amp;W printer) had a tiny line nearer to a corner of the sheet. i looked for such a line on my prints but never found it... so maybe they do, maybe they dont, either that or the B&amp;W printer has a high DPI so that the dots over the sheet are too small, or maybe the dots are now encoded into the way the printer renders shades of grey/colour (called dithering) - which might be present on printers you have previously thought were OK.</p>
<p>Geez man, thanks for the reply, but my above comment is 7 years old, I even forgot what instructables was.</p>
<p>So, for simple text, wouldn't printing with a yellow background obscure the code to the point that it couldn't be detected?</p>
<p><br>Its cool :)<br><br>Tremendous</p>
<p>great</p>
<p>Its really good :)</p>
<p>Thats very good.</p>
<p>Its excellent :)</p>
<p>Awe-inspiring...!!</p>
<p>Thats breathtaking</p>
<p>Outstanding...!!</p>
It's the illuminati, I told them, they never listened. I also don't trust toasters, they probably put crazy tracking sh*t in them too.
<p>nice</p>
<p>Its striking :)</p>
<p>Awe-inspiring...!!</p>
<p>sensational and informative ,thanks</p>
<p>Its interesting</p>
<p>what's with all the bots here? their accounts advertise insurance and cruise websites. they are the ones with single word comments and comment the same stuff on other 'ibles.</p>
<p>super</p>
<p>this is like the NSA spying on our phone conversations</p>
<p>his is wrong in so many ways and quite disturbing as well come to think of it...</p>
<p>Thats sweet</p>
<p>his is wrong in so many ways and quite disturbing as well come to think of it...</p>
<p>Its fabulous :)</p>
<p>Its nice</p>
<p>Thats remarkable</p>
<p>Thats astounding</p>
<p><br>Thats astounding<br></p>
<p>Its extraordinary</p>
<p>Thats cold</p>
<p>Fascinating</p>
<p><br>Its extraordinary</p>
<p>good</p>
<p>GREAT</p>
<p><br>Thats magnificent...<br></p>
<p>great</p>
<p>great</p>
<p>good</p>
<p>good</p>
<p>super</p>
<p>good</p>
<p>Its nice</p>
<p><br>Thats hip<br></p>
<p>nice</p>
<p>good</p>
<p>Very weird and strange.</p>
<p>Its great</p>
<p>good</p>
<p>Its beneficial</p>

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Bio: We are an international non-profit advocacy and legal organization dedicated to preserving the right to freedom of speech in the context of today's digital ... More »
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