Unauthenticated user in mysql processes list - hack attempt?

Question

I see frequently when I run mysqladmin proc or when I review the MySQL Server process list a user marked with: unauthenticated user trying to connect.

+-----+----------------------+--------------+-----------------+---------+------+------------------+------------------+-----------+---------------+-----------+
| Id  | User                 | Host         | db              | Command | Time | State            | Info             | Rows_sent | Rows_examined | Rows_read |
+-----+----------------------+--------------+-----------------+---------+------+------------------+------------------+-----------+---------------+-----------+
| 40  | unauthenticated user | x.x.x.x:xxxx |                 | Connect |      | Reading from net |                  | 0         | 0             | 0         |

What may causes such thing?

Is that normal, or should I investigate my system for any vulnerability or security breach?

Thanks

Answer 1

unauthenticated user is the user connected and not yet sent authentication credentials. Doesn't look like a hack attempt to me.