Printers have an in-built tracing technology. These are Machine Identification Codes (MIC) known as yellow dots, tracking dots, or secret dots. This means that every single page you print can potentially be traced back to you. But how exactly do they work, and why do they exist?
The secret dots are a very faint pattern of yellow dots that printers leave on every single printed page. The pattern, which is roughly rectangular, is repeated across the entire page and indicates the make and model of the printer, the serial number of the printer used, as well as the exact date and time that the page was printed. Think of it as a printer’s digital watermark. For example, using the secret dots, it can be identified that a page was printed on 5th July at 10.53 PM.
These dots are usually spaced one millimetre apart, and are repeated several times so that identification may still be possible in case of errors. Therefore, the printer can be identified even if only an excerpt or a fragment of the printed page is available. These yellow dots are also invisible to the naked eye, but can be viewed by using an ultraviolet light, a microscope, or a high-resolution scanner.
Why Do Printers Have Secret Dots?
Way back in the 1980s, the U.S government was concerned that the newly arriving color printers would be used to scan and forge U.S currency. As a result, Xerox came up with a printer encoding mechanism that would make outputs from printers forensically traceable to assuage the concerns about counterfeit bills. All the major printer companies entered into an agreement to add the secret tracking dots. The public, however, did not become aware of this till 2004 when Dutch authorities used it to track down currency forgers.
Of course, preventing currency forgery is not the only thing these tracking dots are used for. They have been used to catch and arrest government whistleblowers who leak secret information as well. An example is Reality Winner, the person behind the NSA leak, who was identified using tracking dots.
Do All Printers Add Secret Tracking Dots?
Almost all color laser printers add yellow dots, even if you print in black and white or grayscale. You might have noticed your color printer refuses to print documents even in black and white even if one of the color toners (such as cyan, magenta, or yellow) has run out. This is because the yellow toner is required to print the yellow tracking dots.
However, this yellow dot pattern technology appears to apply only to color printers. This is because monochrome laser, inkjet, and LED printers do not have the yellow toner necessary for the dots to be added. Even though monochrome printers cannot add yellow dots, that does not mean that documents printed on such printers are untraceable. It simply means that they probably use a different type of tracking method.
When Are The Tracking Dots Added?
The secret dots are added by the printer hardware after it receives printing instructions from the computer; that is, when the pages are being printed. Therefore, the tracking dots will not have any effect while using other print options such as “Save as PDF.”
Can You Stop The Printer From Adding The Tracking Dots?
No, you cannot. Since the addition of the tracking dots is something that is carried out deep inside the printer hardware, and not controlled by the software on your computer, you cannot do anything to stop it.