It’s been revealed that several laser printer manufacturers cause their printers to print covert codes onto all documents. These codes in the form of small yellow dots cannot be detected in normal circumstances, but using a special blue light, security agencies can use the dots to identify which printer printed a document.
This has raised privacy concerns and allegedly not all manufacturers have installed this feature. As far as can be ascertained, inkjets do not do this.
Sources:
Indymendia
PC World
