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>
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>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>this is like the NSA spying on our phone conversations</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><br>Thats astounding<br></p>
<p>Thats cold</p>
<p><br>Its extraordinary</p>
<p><br>Thats magnificent...<br></p>
<p>Its nice</p>
<p><br>Thats hip<br></p>
<p>Very weird and strange.</p>
Very weird and strange.
Scary facts.
This is wrong in so many ways and quite disturbing as well come to think of it...
I find this just a tiny bit silly, or it it just me?
What about scanned documents? If a document if scanned from any scanner and then saved as a jpeg and sent as an email where the IP cannot be tracked is there any data that can be found then on those jpegs?
WOW! <br>Thank you so much :) You made my day !!
Its usful
sensational and informative <br>thanks
why could not you just print a blank page many times thru different printers ( or print in white something like a period). running it thru top first , then bottom first then thru other printers, it would be hard to tell which printer made which mark making it hard to tell exactly where each mark came from
It's impractical to do so on a regular basis to help prevent being spied upon, but yes, this would cause problems with their system. Congratulations, now the system is only useful for invading our privacy and not preventing fraud. :D
&quot;It's outrageous that manufacturers make secret deals to compromise our privacy.&quot; What privacy? How many times do you send a letter to some one and you <strong>do not </strong> want them to know who sent it? This is not any different than your IP address being included in an email or saved at a website. <br/>
when you print something you expect it to be anonymous unless you intentionally signed it for love letter (do you really want it to be anonymous ?) you probably just print and its anonymous. for some other stuff you may want to use a generic font / shred the text with babelfish / handle the page with gloves. you sure dont want the dots there
The dot's don't identify the person, right? Just the printer. Then this has nothing to do with privacy. The dots will only tell someone that a XXXprinter printed it, not Bob Smith printed it.
scenario 1 your boss asked you to print some stuff for him with deadline. deadline passed and you did not do that. boss calls and asks whyits not ready. you tell him you sent and thats the mail service fault (and not yours). you sit to print it and remember to write there the date of 2 days ago (to make the show perfect) boss recieves the mail. he is freaked off how late the docs arrived and shares his rage with a friend. his friend suggests him to check the true date encoded in the dots and decode that using the calculator in the EFF site scenario 2 you are a journalist who uses the computer for his professional stuff as well as his personal stuff. he prints a doccument that he wants to make confidential so that no one can get on him if the document falls in the wrong hands. the document does a month ago his daughter married an he printed the invitation letters on the same printer. one of those letters is enough to link him to the confidential doc via the printer serial number the dots contain information that you did not intend to include in the document you print and you are likely to be unaware of its existence. this is a privacy issue. no need in your name it may be very complicated to find by incident a titled document printed on the same printer - so it does not look that severe. possibilities become huge when dots meet other info that can be esily crossed with them - like where was batch of printers of model X and manufacture date Y sold - probably available from the manufacturer lets wait for the EFF guy to explain more
Cereleste, you are correct, the information is just Lexmark - serial number xxxx-xxxxx-xxxxxx and perhaps the date and time. This is not printing out your name, address, and contact information. 11010010110: Both Scenarios are possible, but not really probable. Unless that Boss makes it a policy to look at the dots on each page, then he probably would not even think about it. If someone is using a printer for both "questionable" business practices and personal use, he deserves to be caught. Base line point is this: If you are printing something out that you do not want to be linked to in any way what so ever, make sure you have an older printer that does not support the dot printing.
Post Script: This is nothing new. Forensic Detectives used to be able to tell what typewriter was used to create a letter based on the pits in the letters as they stamped into the ribbon and paper. Some companies would even put these pits into their letters on purpose so that it was a form of signature that their typewriter was used.
You do realize there are other ways to tell where a document came from... Forensic scientists and the FBI don't need fancy dots to tell them where a document came from. And if every model has a different method of placing dots, it would take more money and time to develop a database of different methods and then cross check the dots with the database. I don't believe it's worth it. And i guarantee I'll get a scathing reply about "the man" and how "big-brother" is watching, but i still believe that this is the printer manufacturers decision and not the government violating your freedom of speech.

About This Instructable




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 »
More by EFForg:Yellow Dots of Mystery: Is Your Printer Spying on You? 
Add instructable to: