The main source of my confidence is extrapolation from the results of successful initiatives to improve security. Rust is one such initiative: at relatively low cost, it drastically improves the security of "systems software" (defined for our purposes as software in which the programmer needs more control over resources such as compute time and latency than is possible using automatic memory management). Another data point is how much Google managed to improve the security of desktop Linux with ChromeOS.
There's also the fact that even though Russia has enough money to employ many crackers, Starlink's web site continued operating as usual after Musk angered Russia by giving Starlink terminals to Ukraine -- and how little damage Russia has managed to do to Ukraine's computing infrastructure. (It is not credible to think that Russia has the ability to inflict devastating damage via cracking, but is reserving the capability for a more serious crisis: Russia considers the Ukrainian war to be extremely serious.)
Sufficiently well-funded organizations with sufficiently competent security experts can create and maintain a software-based system that is central to the organization's process for delivering on the organization's mission such that not even well-funded expert adversaries can use vulnerabilities in that system to prevent the organization from delivering on its mission.
You seem to be saying ‘secure’ == ‘compromises are able to be fixed’.
Which doesn’t fit any definition of secure I’m aware of.
Every one of those things you mention has been compromised, and then fixed, at various times. Depending on specific definitions of course.
And that is what we see publicly. Typically figure on an order of magnitude more ‘stealth’ compromises.
For a compromise to be fixed, someone has to notice it. Exposing machines to the Internet increases attack surface dramatically. Allowing machines to talk to the Internet unmonitored and unrestricted increases their value to attackers dramatically.
Without careful monitoring, many of the resulting compromises will go undetected. And hence unfixed.
You made a universal statement, namely, "there is no secure software".
If you had written, "99% of software used in anger is insecure," or, "most leaders of most organizations don't realize how insecure the software is that their organizations depend on," or, "most exploits go undetected", I would not have objected.
That is quite explicitly not what I wrote. You might want to re-read my comment.
My point not only stands, but is reinforced by your comments.
If software is eventually compromised, it was not secure. I have yet to see any software that does not eventually get compromised when it gets enough exposure.
That those compromises can get fixed after the fact doesn’t change that.
And ignoring the explicit cases where your examples were disproven doesn’t help your case either.
What makes you think such a thing is possible? In reality, not theoretically.
I also have yet to find an unpickable lock, given the same constraint. Locks still have utility.
But only fools protect something very valuable with just a lock.