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Welcome back to Printing Security Intermediate Course. In this lesson, I'm going toe talk about PCL five paper definition language and how can you have a printer with P C. L's in general,
PCL five uses escape sequins. Common commands so means that if you're sending just the plain text file on the PCL printer, providing that you have a head there and other things that are necessary for modern printer to understand what you're trying to do with a print job.
So if you create a text sprint job with just the text and Heather,
uh, it will print that text like like a regular old style that metrics printer, of course, using default phone to defined by
the device, which is set on the device itself on and
basically a printing default. So resolution and everything else is going to be set to printing default.
Now, if you want to change something like, for example, you want to change the resolution Human to set the resolution to be 600 by 600 dp I or you want to use some kind of resolution enhancement technology that modulates the size and the position of the dot on the paper to get the crisper output,
um, or you want to add some graphics. Then you have escape sequences, which you start with a ski 27 character.
And then what follows? That escape character is basically a PCL five command and then printer interpreted the command
in the way it is defined in the description of the Printing PCL language. It's not a real programming language, so there is quite the limitation of what it can do.
And the process off Processing PCL five document print file in the printer is called Parsing, So you are not running it like a regular print language is just that. The software inside the printer, which is
PCL five part sir, is looking at commands and putting something in the memory
that, ah,
we'll be later transferred into dots on the paper.
So in generally, if you have PCL, regardless of aversion, how do you hack with it? Well, you can intercept and alter
print jumps, or you can create malicious prince files by yourself,
and what you can do is essentially change the white settings. Now these changes can be serious. For example, you can do a device reset so that whatever is in, ah, devices, memory can be deleted. Uh, although it's usually done with P J L not with PCL,
but you can do, For example, you can change the message that is on a display, which says, Ah, error device users basic. Put it in the port. Whatever. And that way you can fool a user to hack a device or something like that.
And if you want to look more into PCL hacking, you can download the practical, which is essentially a reference for printing, hacking Using PCL. You have the address here, you can download it, install it and play with it and see how it's done.
So in this video, you have learned that what are the specifics of PCL five and what can you do if you want to hack a printer using the seals
in next lesson, I'm going to talk about PCL six and the differences between PCL six MPC or five
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