There are myriad bits and bobs of software and services that promise to do anomaly detection in logs, but an easier approach for now is to just move ssh off 22. It affords basically zero extra real security but makes any subsequent login attempts more worthwhile to look at.
Broader answer after reading some of your other comments in this thread: in your ideal, highly secured network environment, none of this is necessary because everything's wired up tighter than a gnat's ass hole. Unfortunately I've never had the pleasure of working for one of those places.
The networks I'm describing aren't "ideal" or "highly secured". I am describing table stakes. While I was at Latacora, most of the clients we engaged with were already at this level of maturity when we joined up.
> The networks I'm describing aren't "ideal" or "highly secured". I am describing table stakes. While I was at Latacora, most of the clients we engaged with were already at this level of maturity when we joined up.
One of the most valuable things you do here is describe things that you believe are table stakes to people and organizations that have never heard of them. Companies like Latacora tend to self-select for clients that are at least aware that security should be a sensible line item in their quarterly budget. There are many many more organizations for whom moving ssh or even port knocking amount to a real improvement to their infrastructure. :-(
https://canary.tools/help/canarytokens
But the concept is really simple: come with any kind of thing you'd want to tripwire --- the AWS key is particularly slick --- and put it somewhere in your infra, then wait for alerts.
What if the attacker does not use software that automatically loads images, like the "canary token" tracking pixels?
What is the attacker opens the files offline?
Canary tokens still work? How?
Why would anyone advise using canary token instead of port knocking? Makes no sense. Why not use both?
thankfully, i dont have properties which attract determined scanners. and i imagine that's true for 99% of public ip addresses, too.
even if security through obscurity is not real protection from targeted attacks, it is at minimum significant noise reduction, and quite possibly a reasonable barrier against drive-bys which assume default configurations. i'm sure you know how many scanners try to access some default php/wordpress admin route. how much of that would disappear if wordpress was simply installed behind a random 32-char route instead of /wp-admin? all it is is obscurity, sure. but is it not security?
I call BS. These are pretty much the same thing* which is to say: an adversary trying to get the file needs to know something that they don't know, and can't reasonably guess/discover any time soon. Did you secure it or obscure it? Whatever you call it, you require a "something you know" factor.
*Obviously, there's the fact that other parts of the stack -- browser history, access logs, rate limiting, etc. -- actually treat a password payload with the respect it deserves and assume there's nothing sensitive about a URI path... kindly pretend my example doesn't have this flaw.
You may accidentally enable the directory listing.
While you may say that certain methods of withholding the information are isomorphic at certain conditions it doesn’t mean that they are semantically equivalent.
Every exposed 22/tcp on the Internet is being continuously exposed to automated SSH scanners running from thousands of points on the Internet. There is nothing you can reasonably do to prevent it (the sources are so diverse you couldn't even realistically block a determined scanner), and, if you've turned off password authentication --- which you must do anyways --- the probes aren't a meaningful threat.