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We get asked reasonably often if it's possible for a sysadmin to set up PuTTY saved settings and then lock them, in such a way that their users wouldn't be able to fiddle with them.
It's not, and I (SGT) don't intend that it ever should be. This is for two reasons.
For a start, it seems to me to run counter to the whole point of software, and certainly the whole point of PuTTY in particular, which is to enable people to do useful things. The reason I give my free time to develop PuTTY is because I enjoy making it possible for people to do things they otherwise would not have been able to do - and judging by the mail we get back from happy users, they enjoy it too. So adding a feature which would allow someone to stop people from doing things they otherwise would have been able to do seems to me like a step backwards.
Secondly, it wouldn't even work; or, at least, it wouldn't work in all but the most ludicrously restrictive setups. The reason for this is that this sort of restriction is voluntary on the part of the application - so all a user would need to bypass it would be a modified version of the application, which didn't voluntarily obey the restrictions. And this wouldn't be hard to come by; even commercial, closed-source programs which try to restrict users from doing things give rise to cracking tools, distributed on the Web and designed to bypass whatever restriction was imposed by the software. A program whose source code is freely available to anyone with a web browser would be an order of magnitude easier to do this to. I confidently predict that if I implemented a user-restricting feature in PuTTY, then it wouldn't take long for someone else to provide a version for download which simply ignored the restrictions. So the only environment in which a restricted PuTTY would actually be secure would be one in which the user was somehow forcibly prevented from installing an unrestricted version.
(Even locking the Registry itself against updates wouldn't protect you against a version of PuTTY which had been modified to store its data somewhere else. Really, your only chance of success is if you completely prevent users from running any binaries except the ones you supply.)
In summary: if I have my way then PuTTY will not implement a voluntary locking mechanism. Any sysadmin who really, really wants such a thing can of course modify the source code and implement it themselves, and take whatever precautions they feel necessary to ensure users don't download the original version and bypass the restrictions; but I don't feel that it's an appropriate use of the PuTTY team's time and effort, or an appropriate use of space in the standard PuTTY binary (which we're still trying to keep small).