What causes this SSH message?

[Steve Snyder <swsnyder home com>]

In /var/log/secure I get a couple of these each day:

Dec 27 11:57:17 sunburn sshd[9039]: Did not receive identification string 
from 0.1.2.3.

The time and actual IP address in each message varies.  Note the address 
are not recognized by me.

I am puzzled about what sshd is telling me.  It appears that these messages 
indicate failed login attempts, yet when my fat fingers hit the wrong keys 
during login I get a message about authentication having failed, not lack 
of ident string.

What is sshd telling me with this message?

Thanks.