Picture of Yellow Dots of Mystery: Is Your Printer Spying on You?

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

Picture of 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.

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lujanmarion2 years ago
rickafost2 years ago
sensational and informative
itsme1236 years ago
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
vov35 itsme1233 years ago
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
"It's outrageous that manufacturers make secret deals to compromise our privacy." What privacy? How many times do you send a letter to some one and you do not 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.
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.
But such a database would connect a document to a model of printer, not to an individual printer, as the coded dots do. Nothing to do with big brother watching or free speech. The USA darn nearly descended into McCarthyism, with no respect for the bill of rights, post 9/11. No need to give the government more tools to harass anyone that doesn't tow the nationalists line.
vov35 static3 years ago
most high value electronics have a unique serial number. they can identify the specific printer that this came from.
The government doesn't harass those that don't "tow
not  true the fbi created the method... i fix copiers.  no color copier is allowed to be sold in the usa without this dot pattern encoded in the image it is created in the print engine not from the image process even when the machine is internaly calibrating itself these dots are formed and visable  on the transfer belt  the only information encoded  in the dots is model numbers and time and date that way if a faudulent document is found it can be traced back to the source ...one day the fbi showed up and took an entire machine as evidence when some funny money showed up...BTW most high end color copiers can detect money being prited on them and will actually code to the point where your local rep cant fix it and a rep from the manufacturer has to come in and reset it  ...that how deep the rabbit hole goes my friend  for the manufacture i represent there are only 4 people in the usa that can reset that code
Then why ask the printer companies to institute the yellow dots, if they don't need them? And if they asked them to include this technology, then don't you think they maintain a comprehensive database of what the dots mean? It's not like Xerox/XP/Canon etc. has a vested interest in what you print.
i think the effort it would take to maintain a database of yellow dot patterns outweighs the benefit. To answer your question, no i don't think the government maintains a database of yellow dot patterns, and Xerox, HP, Canon, Brother DO have a vested interest in what you print, or rather how you print.
You are correct, this is not something that the government has in created, it is only a digital signature of the printer. Now if someone were to say print off a threating letter and send it to someone, then this could be used to help track the person in question down. But just by looking at the dots on the page would not be all that it takes.
my point exactly.
Comparing apples to oranges. The detectives have to have both the document and typewriter in hand to connect the document to a typewriter, and the typewriter to an user. Same goes for using old school methods used to match a document to a printer. Now only the document is the only thing needed to connect it to a specific printer.
out of curiosity what does your name say in binary?
ash? Then why does my binary translator says you are Ò ?
11010010110 --> 10100101 --> A5 (hex) --> A5h --> Ash
Nice! Why do you trim the "1" and "10" though? Signal start/end?
I know of at one count of the operator being identified and convicted by comparing the operator log with the time stamp in the code. I serviced one particular color printer that included firmware to recognize currency. We were warned, sternly, during training that we should NOT attempt it. The instructors stated that they did not know how the firmware worked or how it affected the printer. Since it was a network printer it had the capability of reporting such attempts.

I typed that link freehand, but it probably works
Not only that, even my scanner (canonscan lide 90) can't scan currency (tried it Euro). What is the logic in that??? So I can't send pictures of money? I should return it to the shop.
wow ! this story with firmware just shows how the _government_ is paranoid what make and model is that printer ?
Xerox - I worked for them 33 years. The technology is used in mostly color and all models have something similar. The quality was so good that copies would be accepted by scanners. Something had to be done to prevent counterfeit.
Yes, So smash your printer with a hammer, and print at the library. Except it's still an invasion of your privacy.
However if you send in your warranty card, your privacy would be compromised. Your choices. Rick that the product you buy isn't a lemon, and don't send in the card. Protect you pocket book, by risking your security. Today merchandise can be trace from factory to retailer. Not a stretch to imagine the trace from retailer to purchaser. I fail to trust that every bar coded item I purchase is not link to my checking and/or CC accounts. Paranoia? Perhaps, how can we know for sure?
bar codes are not an issue - they are the same on all stuff of the same type you'd better go google on RFID :) many new printers come now with online registration feature in the setup wizard. im sure this registration includes serial # of the printer and some data from the computer we have one such printer / scanner combo from HP and the thing is quite annoying (with options only 'now' and 'later' and cannot be disabled. it gets back to startup when you use the scanner)
So, invading your privacy is ok, since you've go nothing to hide, right? I'll be sure to hack instructables to get every thing I need to know about you to eliminate your intellectual life, get you locked illegally in a government facilty, And have your family and friends searched and bugged. Still Sound like a good Idea?
It's very different actually. Just because we are all spied on while surfing the Internet in the name of security, does not mean that should spread to any other area's of our lives. It is outrageous.
Grimmiger4 years ago
I just love how so many people are getting paranoid about the government watching everything we do and print!
It is not for that.
It is mostly used with services such as law enforcement to be able to identify if a certain note or letter was printed from a certain suspects printer. Also it allows other agencies to determine if it is actually from where the letter says it is from.
Think of it as more of a personalized watermark.
Please do not reply to this comment if all you have to say is the government are out to get us.
vov35 Grimmiger3 years ago
Law enforcement isn't the government or anything.
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