What do these log entries mean?

[Philip Mak <pmak@xxxxxxxxxxx>]

Apr 29 17:37:08 lina telnetd[15972]: Connect from 200.163.59.156
Apr 29 17:37:09 lina telnetd[15972]: ttloop: retrying
Apr 29 17:37:09 lina last message repeated 1474 times

That was in /var/log/messages. Then at 17:37:10, there was an
unauthorized login to the "nobody" account.

Also:

Apr 29 16:52:54 lina telnetd[5427]: Connect from 200.163.59.156
Apr 29 16:52:58 lina telnetd[5427]: ttloop: retrying
Apr 29 16:52:59 lina last message repeated 28989 times

And there was an unauthorized login to "nobody" at 16:53:00 too.

And I don't have telnet enabled on my server (I tried telnetting to
double-check, and got Connection refused as expected), so I'm confused
as to why it says "telnetd". Anyone have an idea how he's getting in
to my server?
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