This is interesting. As regular user of crypto I would have never imagined that there is stuff like this. In fact this was new learning for me and made me think I should be extra curious about my private keys. Anyways, I am guy who after creating an address would think thrice which key is to be shared to public and which one not even when they mention in BOLD which one is private key and public key. Idk, there might be many of such users out there doing the same thing to avoid what has happened / mentioned in the OP.
I assume many people have systems monitoring all compromised private keys, and they're competing against each other to steal the funds before someone else does. Back in the days, it happened to large amounts of Bitcoins, but the more recent transactions are mostly small. Except for last month (January 24): this address received 0.84362383BTC, which was instantly sweeped. The private key was posted 2 months earlier:
I am surprised to read this. What kind of systems are these? How are they able to monitor if a private key is leaked or not. Its confusing to understand and it should be known to everyone so that I won't be making the mistake of leaking my private key by accident.
For example, whether it is phishing sites, or a software downloaded from play store, or any browser extension? What kind of monitor? & how does it recognize the gibberish code as pvt key anyways?