Stopping Screengrabbing

[Kzin]

As a sort of flip side to my other question does anyone know how to stop screengrabbing applications (or even better to over-write a watermark onto whatever is grabbed)

capture the print screen button being pushed, then grab whatever was copied from the clipboard, watermark it, and copy it back.

Z.

[Kzin]

Does a screen grab necessarily go through the clipboard?

When its done with print screen, yes.

Z.

[Kzin]

It there an event that I can trap to detect when a clipboard event happens?

[PsychoMark]

This code will provide an event for changes in the clipboard:

http://www.vbaccelerator.com/codelib...p/custclip.htm

Although it won't work if the capture program doesn't use the clipboard...

[Kzin]

Thanks - very useful

[Kzin]

Still got a problem with this one as it does not stop screen grabs through things like Paintshop Pro

Any thoughts on how to stop that one?

[PsychoMark]

This topic has been discussed many times, and every time the answer was: there's no possible way!!

You can stop clipboard copying with techniques like these, but once something appears on your screen it is not save against screen grabbing....

Well, you can offcourse disable the mouse and keyboard input, but hey, just write a macro which moves and clicks the mouse and you've still got a screenshot


My point: don't try preventing it. If you want something to be save from copying, don't publish it...

[Nirces]

I have to ask why would you want to?

also if your using a combined image based Watermark, then display it on the screen then it will be captured aswell.

[Kzin]

Originally posted by PsychoMark
This topic has been discussed many times, and every time the answer was: there's no possible way!!

There are obviously lots of *possible* ways such as having the software kill unrecognised tasks or processes, scanning memory for recognisable copies of screen memory, intercepting the API calls used in capture - the question is which is implementable and how best to do it - which is why I'm asking. Like most security related tasks this is probably something that needs multiple solutions. There is a lot of pooled skill on this forum and not everyone reads every message every time so it is often worth asking again.

Originally posted by PsychoMark

My point: don't try preventing it. If you want something to be save from copying, don't publish it...

Presumably you have door locks, use encryption, hide your credit card in a fold of dead animal skin and maybe even hide your source code - don't you know that there's no possible way to stop physical theft!!

don't try preventing it


Seriously guys - there are many very good reasons why you might want to deter or make non-trivial the capture of screen content - which may include content that cannot be watermarked such as scrollable text screens and databases. Not all information is zero value and not all information thieves are technically sophisticated so this is very much a real question.

[Sastraxi]

Well think about this: hardware cursors never get screen-grabbed... can you guess why? They are made on the hardware, never blitted to the screen, just overlayed on top of everything. You can never get it's position, (well you can if it's a mouse) and can never get the colour bits. But you can set all of these up. Unfortunately I don't know how to do this.

Also you can't grab a directdraw proggie when done in a certain way, but I have no idea what that way is, sorry.

[PsychoMark]

Ever heard of HyperSnap DX?

(it's a screengrabber which additionally can grab many DX surfaces and Glide surfaces...)

[HarryW]

What kind of information could you brand someone an 'information thief' for recording independently, yet you would be perfectly willing to show it to them in the first place? That is an honest question, I am assuming you have an answer for it and want to use this for some real reason.

Personally, I would be very annoyed, as a user, if an application tried to prevent me from capturing screenshots of what I was looking at, it would be like a hostile takeover of my computer, a loss of control. There will always be a way to record the images displayed on the screen, although you could make it pretty difficult I suppose.

[Fox]

There will always be a way to record the images displayed on the screen, although you could make it pretty difficult I suppose

I fully agree, as long as you can see a picture or hear a music you won't ever be able to protect it from being recorded. It's the same with audio-CD copies, you can always record the music from the cd (connect line-out and line-in ) and burn this again.. NO WAY to prevent this

[/\/\isanThr0p]

to the hypersnap DX thing that was posted earlier. I just make the guess that it doesn't grab the cursor, but gets it position, finds the cursor and draws it itself over the earlier grabbed picture.

Well if anyone want to make some routines against saving pictures displayed on screen -- HAVE FUN. (there are only ways to make it harder)

Hm what do you guys think of a hardware overlay that cycles colors (under dos that would be possible dunno about windows) those screenshots would be all messed up at least.

[Kzin]

Originally posted by HarryW
What kind of information could you brand someone an 'information thief' for recording independently, yet you would be perfectly willing to show it to them in the first place? That is an honest question, I am assuming you have an answer for it and want to use this for some real reason.

Personally, I would be very annoyed, as a user, if an application tried to prevent me from capturing screenshots of what I was looking at, it would be like a hostile takeover of my computer, a loss of control. There will always be a way to record the images displayed on the screen, although you could make it pretty difficult I suppose.

Here are some real examples

In medical and clinical research you can publish internal reports of *possible* problems that can be assessed by professionals without being spread to the media or lawyers. These are often the sort of issues that might not be assessed at all otherwise for risk of leakage and litigation.

In environmental risk assessment you could send graphs & data about of problems building up within organisations without the risk of being branded as a mole or being the source of a verifiable leak - information that many users would otherwise keep to themselves if they want to keep their jobs/careers.

Financial information is often transmitted in real time to selected individuals who may be privy to that information for specific reasons and not allowed to pass it on or reuse it. (There are reams of laws on insider trading etc that relate to this sort of thing)

Remember the data is often more valuable than the computer in these cases. In all cases the information could be remembered, written down, photographed from the screen etc but this is another layer of difficulty for the 'information thief' and put the communcation more on the same footing as a confidential phone cal rather than an open invitation to publish.

[chilibean]

I have no idea how it works, but Clever Content successfully protects images on web pages. There is absolutely no way to grab the image using normal methods (and I even tried a program using APIs). If you want to check it out just go to http://www.clevercontent.com/ and see for yourself. Print screen fails, Netmeeting fails (you get a nice message asking you to close the program), APIs fail, and most graphics grabbers fail. The only way I could capture the images was using a camera aimed at the screen.

By the way, if any of you know how this works I would be very interested to know.


chilibean

[Nirces]

There is No way to stop infomation being captured.

(Hmm the ultimale Stopper, but i really want it... ohwell, looks like i will plug my video out into my video and just record it.) Try to stop that!

you can make it hard.

if you wish to use CopyMemory(), you can copy a custom Function you wrote into an Apps Copy of the API its using, making it call your function instead the API, you could then call the api yourself, do whatever to the image then pass it back (only works on NT, 2K, 98,ME you would need to modify the internal/external

Best ways to go around it are:

Bad Colours, Putting a Fractal Red Design, simlar to the text colour, so you can read see the infomation, but printing creates a mess.

the only way to do it properly, if your that concerned about data leaks, is Specilist Hardware, example, a Laptop made to decyrt Images sent via a Com port and Display them, with the keyboard, Video out and everything else not needed Ripped out. with software in the system to see if it has been tampered with. (ie like another device added. With a custom Operating system onit.

goodluck

[Kzin]

Originally posted by Nirces
With a custom Operating system on it.

Yes - I'd already thought of a custom crippled linux kernel and shell - no need to have custom hardware for that - that would be a heavier weight solution.

[Kzin]

Originally posted by chilibean
I have no idea how it works, but Clever Content successfully protects images on web pages. There is absolutely no way to grab the image using normal methods (and I even tried a program using APIs). If you want to check it out just go to http://www.clevercontent.com/ and see for yourself. Print screen fails, Netmeeting fails (you get a nice message asking you to close the program), APIs fail, and most graphics grabbers fail. The only way I could capture the images was using a camera aimed at the screen.

By the way, if any of you know how this works I would be very interested to know.


chilibean

This is more like it - this would be the target to emulate - but how?