Hello Matthias,
assuming you tried to log in from an IP address assigned to DTAG and used for dial-up-purposes (80.144.x.x), there have been indeed four failed SSH login attempts from it on Sunday morning (~ 08:00 CET).
The same IP address caused one failed SSH login attempt again yesterday, at 15:56:44 CET, but did not exceed the limit this time. :-)
Sorry for the inconvenience.
Thanks, and best regards, Peter Müller