Could well be. I haven't messed with Win32 in a while, but I'm pretty sure that you can sniff the contents of other applications' windows and dialogs. With a little work, you should be able to take a common app and work out how to detect it's login windows, find the username and password and other relevant fields, and pull out the contents.
I know if I was writing a hostile keylogger, I'd go to a lot of trouble to know exactly what was entered where, instead of having to see a long stream of keyboard input and figure out what the usernames and passwords are, and what services they go with.
The most obvious way is to hook the message stream from the window manager to the applications, windows provides some convenient hooks for this.
Whereas, I believe if you go by your second point, you can see "Ok, the user put username <x> in the username textfield, password <y> in the password field, address <a> in the address textfield, port <p> in the port textfield" and so on, which would make for a more structured data dump. Maybe not possible or feasible for every single application, but if you could get the highest usage targets, like the most common FTP clients, or Steam as they have apparently done, and the browser password storage stuff (or fields for say, most common banking sites, PayPal, etc.) then you could save yourself a lot of time.
{TAB}{TAB}{CURRENT WINDOW: Steam - Log in}{TAB}username{LEFTCLICK}password{LEFTCLICK}{CURRENT WINDOW CHANGED: Steam: Home}
FileZilla simply use a file in your personnal directory to store passwords exactly like your browser too.
- how do those PW stealers work? are they similar to the Steam one, where it'd delete existing creds and then sniff newly entered ones?
- can this thing detect certain apps like FileZilla and then say "user entered <FTP site creds>" and send individual fields, and is that what is meant by supporting say FTP and FileZilla?
- what does PHP support mean? maybe looks for common stuff like php.ini, various other conf files like FPM, and tries to find DB/cache connection creds?
there's one other thing I'm wondering about, which is the light/easily crackable encryption of the keylogger's internals, and I vaguely remember reading about Google's encryption on the new recaptcha and people talking about all this stuff like complicated encryption routines baked into the client side JS that I really didn't understand except at a handwavy level, and wonder if that's the kind of thing some, say, intelligence/espionage outfit could use.
very interesting/engaging (fun) article, all in all, for me. and I appreciated the understatement of the (well-deserved) plug at the end.