Re: Turning off screen shot ability
Re: Turning off screen shot ability
- Subject: Re: Turning off screen shot ability
- From: "Brad O'Hearne" <email@hidden>
- Date: Wed, 06 Mar 2013 09:37:36 -0700
I appreciate the desire of a few here to communicate your perceived futility of turning off screen shots or window capture. I do not want to digress into a philosophical discussion here, I just want to stick to talk of the capabilities of machinery -- but given that the responses here pretty much scan with the discussions I found at various forums online, I want to just briefly address the futility issue.
Because a security measure can be breached, either in common practice or in theory, does not mean that it is either futile, or that it is wise to just throw it away. I could give a very long list of examples of this, but for brevity, just a few:
- Passwords can be breached, but yet we still actively use and recommend using them.
- SSL can be breached, yet it is the protocol foundation for most secure communication on the Internet.
- An ATM pin can be breached, yet all of us are no doubt happy that our banks didn't just issue us code-less cash cards which pull directly from our bank accounts.
- Car and house locks can be quite easily breached, but yet we still continue to put them in cars and house doors.
Finally, every security system on the planet can be breached by social engineering. Given that there may be no such thing as a 100% secure system, does that mean it is wise to throw off security measures? No. Eliminating 99% (or 90%, or 80%) of potential breaches is useful. Even slowing down a breach is useful on a number of levels.
I would like to avoid everyone's personal editorial on the value of turning off screen capture is or not, as it is a foregone conclusion that we need this in place. My client is in the security business, and while the details of their product are not going to be discussed here, suffice to say, their use case is a completely legitimate pursuit of turning off screen capture -- and that is with full consideration of alternate means of capture, not ignoring them.
So that said, to retrench back to the original question, I am interested in the capabilities of the machine (OS X) and if so, how. I need to programmatically within an app (not by external system administration) turn off all screen capture capability, by hotkeys, or by grabbing the contents of the window. For those who have mentioned screen capture apps as a way to breach this, you might be interested to know that with one common screen capture app (I tested with ScreenFlow) that setting the NSWindow's sharingType to NSWindowSharingNone prevents it from capturing the active window. The primary hole appears to be OS X screen capture hotkeys, and in that regard, I'm really interested why setting the sharingType to none, which is supposed to prevent other processes from capturing the contents of the window (and does in some cases) allows OS X to still capture the screen.
To distill it -- does OS X have the programmatic ability to turn off screen capture, and if so, how? It is just a question of whether the machine can do it or not. While I appreciate the other sentiments, I can assure you this use is completely legit. Either OS X has the ability or it doesn't -- that, and how it is turned off (if it can be) is all I need to determine. One other responder said that he's encountered other apps which *can* do this, so if someone in the know could pass on the 4-1-1, I would be very appreciative.
Thanks in advance,
Brad
On Mar 6, 2013, at 12:51 AM, Izzy Fraimow <email@hidden> wrote:
>> Would you be so kind as to elaborate on your statement, i.e. the "fundamental stupidity"?
>
> I didn't make the original statement but perhaps I can shed some light. Even if, hypothetically, you were able to disable the cmd-shift-3 keyboard shortcut there many, many other ways for a person to capture screen contents. There are 3rd party apps for screen capture, they could mirror the screen and put a sniffer on the video cable, they could eavesdrop on the EM radiation given off by the monitor and recreate the image inductively (yes, this has been done), to say nothing of the most obvious issue: cameras, which are bound to be almost every pocket you come across. There're also screen readers and other assistive devices that expose the same information. Attempting solve any of these "problems", let alone all of them, is a losing battle and would only serve to frustrate legitimate users.
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