Doug WebbMar 2, 2020

Today I learned that many/most color laser printers layer an array of yellow microdots on top of documents 🔬

This Machine Identification Code https://en.wikipedia.org/wiki/Machine_Identification_Code encodes a print date and a serial number unique to the machine. It only became public knowledge in 2004, ~20 year after deployment 😑

The Technical University of Dresden released a tool 2 years ago to layer on _even more dots_ to render the MIC unreadable and aid whistleblowers publishing https://github.com/dfd-tud/deda ✊

Machine Identification Code - Wikipedia

Show threadC24h29ClO4Mar 15, 2020

@douginamug so, this is really cool but it isn't universally applied to ALL prints from a colour laser.

What I've found is that colour laser printers at work won't print these for black and white docs - i suspect this is common since these dots are usually printed in yellow and you don't wanna spin up the colour laser elements if it isn't a colour print job. (it takes ~20 seconds longer to get ready to print colour than it does b+w)

Show threadDoug WebbMar 15, 2020
@c24h29clo4 Interesting! Will have to check that out. Housemate managed to identify them on a print, but not sure if he used color...
Show threadC24h29ClO4
@douginamug keep in mind, these are corporate machines on a printers-as-a-service contract. No guarantee the feature isn't disabled to save toner or otherwise comply with business or legal privacy rules. I have definitely seen the dots around, just much less frequently on like, bulk letters and similar
Mar 15, 2020 at 1:28amWeb
Show threadAlex@rtnVFRmedia Suffolk UKApr 5, 2020

@c24h29clo4 @douginamug
@Siphonay

I've searched with UV torches and magnifiers for and /not/ found them on a variety of colour printers at work (also on similar contracts) - its possible this method is less often deployed on units outside the USA due to different privacy laws and there being other ways of preventing a printer being used for blatantly illegal purposes such as priinting a banknote,fake ID papers or event tickets (which used to be a thing in the 1990s)

Show threadDoug WebbApr 5, 2020
@vfrmedia @c24h29clo4 @Siphonay we found them on prints from our Xerox Phaser 6510 (Germany)