Printers and privacy and security

What are your thoughts about printers and privacy/security?

Most printers nowadays had related programs. I wonder if they may somehow conntect with online servers to share what I print.

Even if not, there is some chip in the printer. How long data is stored there?
Let’s say I print something privite on my printer even using Linux, than I go to Windows.
Can somebody download what I printed using some virus?
What if somebody has physical access to the printer? Can data be downloaded from the chip?

I also heard many years ago that it is possible to identify printer just by printed ink/fonts. Does anybody heard about this or is it a myth?

If there is a chip in your printer that stores what you printed out (e.g., to print it again), then this may depend on your printer model.

This also depends on your printer model. Some printers come with “advanced” features like Bluetooth and Wi-Fi, so they run more software which results in a bigger attack surface.

The general rule is: If somebody has physical access to any of your devices, assume that the device is completely compromised.

This isn’t a myth. It is called “Machine Identification Code” (MIC).

It is stated that MIC refers to laser printers, are ink ones not identificable?

It may be the case. There is at least one German article talking about tracking dots regarding inkjet printers: https://www.druckerchannel.de/artikel.php?ID=2972&t=machine_identification_code_bei_tintenbasierten_druckern_und_aios

The EFF tried to list printers that don’t print yellow dots (this list is now unmaintained). They state:

REMINDER: IT APPEARS LIKELY THAT ALL RECENT COMMERCIAL COLOR LASER PRINTERS PRINT SOME KIND OF FORENSIC TRACKING CODES, NOT NECESSARILY USING YELLOW DOTS. THIS IS TRUE WHETHER OR NOT THOSE CODES ARE VISIBLE TO THE EYE AND WHETHER OR NOT THE PRINTER MODELS ARE LISTED HERE. THIS ALSO INCLUDES THE PRINTERS THAT ARE LISTED HERE AS NOT PRODUCING YELLOW DOTS.

For tech-savvy people, this project may be interesting: https://github.com/dfd-tud/deda (DEDA - tracking Dots Extraction, Decoding and Anonymisation toolkit)