Looks like only B&W printers might be safe? -Stu
Experts discovered something of interest: yellow dots in a roughly rectangular pattern repeated throughout pages printed on color printers. These yellow dots, magnified 60 times, were found on a Xerox printout. (Credit: Electronic Frontier Foundation)
Here they are on an actual printed document.
They were barely visible to the naked eye, but formed a coded design. They show up better under a blue led light. After some quick analysis, they seemed to reveal the exact date and time that the pages in question were printed: 06:20 on 9 May, 2017 – at least, this is likely to be the time on the printer’s internal clock at that moment. The dots also encode a serial number for the printer.
The Electronic Frontier Foundation (EFF) maintains a list of colour printers known to use them. The images below, captured by the EFF, demonstrate how to decode them:
A statement from Electronic Freedom Foundation sums it up well:
Some of the documents that we previously received through FOIA suggested that all major manufacturers of color laser printers entered a secret agreement with governments to ensure that the output of those printers is forensically traceable. Although we still don't know if this is correct, or how subsequent generations of forensic tracking technologies might work, it is probably safest to assume that all modern color laser printers do include some form of tracking information that associates documents with the printer's serial number.
(Added 2017) 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 is a partial list of printers that do this. Is yours on here?
brand model
Brother HL-4200CN
Brother HL-2700CN
Canon Imageclass MF8170C
Canon Color Laser Copier 1150
Canon Color imageRUNNER C3220
Canon Color imageRUNNER C3200N
Canon Color imageRUNNER C3200
Canon Color imageRUNNER C3100CN
Canon Color imageRUNNER C2570
Canon CLC-iR 3200-C1
Canon CLC 5000+
Canon CLC 4000
Canon CLC 3002
Canon CLC 2400
Canon CLC 1000
Dell 5100CN
Dell 3100CN
Dell 3000CN
Epson AcuLaser C900
Epson AcuLaser C4000
Epson AcuLaser C3000
Epson AcuLaser C1900
Epson AcuLaser C1500
Epson AcuLaser C1100
Hewlett-Packard Color LaserJET 9500MFP
Hewlett-Packard Color LaserJET 9500HDN
Hewlett-Packard Color LaserJET 9500
Hewlett-Packard Color LaserJET 5550DTN
Hewlett-Packard Color LaserJET 5550DN
Hewlett-Packard Color LaserJET 5550
Hewlett-Packard Color LaserJET 5500HDN
Hewlett-Packard Color LaserJET 5500DN
Hewlett-Packard Color LaserJET 5500ATN
Hewlett-Packard Color LaserJET 5500
Hewlett-Packard Color LaserJET 5100CN
Hewlett-Packard Color LaserJET 4700DTN
Hewlett-Packard Color LaserJET 4700DN
Hewlett-Packard Color LaserJET 4700
Hewlett-Packard Color LaserJET 4650DTN
Hewlett-Packard Color LaserJET 4650DN
Hewlett-Packard Color LaserJET 4650
Hewlett-Packard Color LaserJET 4600N
Hewlett-Packard Color LaserJET 4600HDN
Hewlett-Packard Color LaserJET 4600DN
Hewlett-Packard Color LaserJET 4600
Hewlett-Packard Color LaserJET 3700N
Hewlett-Packard Color LaserJET 3700DN
Hewlett-Packard Color LaserJET 3700
Hewlett-Packard Color LaserJET 3600DN
Hewlett-Packard Color LaserJET 3550
Hewlett-Packard Color LaserJET 3500
Hewlett-Packard Color LaserJET 2840
Hewlett-Packard Color LaserJET 2700N
Hewlett-Packard Color LaserJET 2680
Hewlett-Packard Color LaserJET 2600N
Hewlett-Packard Color LaserJET 2550N
Hewlett-Packard Color LaserJET 2550L
Hewlett-Packard Color LaserJET 2550
Hewlett-Packard Color LaserJET 2500N
Hewlett-Packard Color LaserJET 2500L
Hewlett-Packard Color LaserJET 2500
Hewlett-Packard Color LaserJET 1600
Hewlett-Packard Color LaserJET 1550L
IBM Infoprint Color 1464 PS3
Konica Magicolor 7300
Konica Magicolor 5450
Konica Magicolor 3300
Konica Magicolor 3100
Konica Magicolor 2450
Konica Magicolor 2430 DL
Konica Magicolor 2400 W
Konica Magicolor 2350 EN
Konica Magicolor 2350
Konica Magicolor 2300 W
Konica Magicolor 2300 DL
Konica Magicolor 2210
Konica Magicolor 2200 DL
Konica Ikon CPP500E
Konica Colorforce 8050
Konica Colorforce 1501
Konica Bizhub C350
Konica Bizhub C252
Kyocera Mita KM-C2230
Kyocera FS-C8008
Kyocera FS-C5030N
Kyocera FS-C5020N
Kyocera FS-C5016N
Kyocera C2630D
Lexmark C912
Lexmark C910
Lexmark C760
Lexmark C752N
Lexmark C752
Lexmark C510
Panasonic Workio KXCL-500
Ricoh Infotec/Danka ISC 2838
Ricoh AP 206
Ricoh Aficio CL 7000
Ricoh Aficio CL 6010
Ricoh Aficio CL 3000E
Ricoh Aficio CL 3000
Ricoh Aficio CL 2000
Ricoh Aficio 1232C
Ricoh Aficio 1224C
Samsung CLP35
Samsung C3210
Toshiba FC70
Toshiba FC25Pi
Toshiba FC25P
Toshiba FC22i
Toshiba FC22
Toshiba FC15i
Toshiba FC15
Toshiba eStudio 3511
Toshiba eStudio 311c
Toshiba eStudio 310c
Toshiba eStudio 3100c
Toshiba eStudio 211c
Toshiba eStudio 210c
Toshiba eStudio 2100c
Xerox WorkCentre M24
Xerox Phaser 790
Xerox DocuColor 6060
Xerox DocuColor 5252
Xerox DocuColor 40
Xerox DocuColor 3535
Xerox DocuColor 2240
Xerox DocuColor 2045
Xerox DocuColor 2000
Xerox DocuColor 1632
Xerox DocuColor 1521
Xerox DocuColor 12
Xerox WorkCentre Pro (all