According to Wikipedia "MySQL is the world's second most widely used relational database management system (RDBMS)
and most widely used open-source RDBMS"
The flip side of this popularity is high number of various brute-force tools that are easily available on the Internet.
Your MySQL Server might be at risk if it allows remote connections. Just look at the Application event log,
there should be the entries like below:
Traces of MySQL brute-force attempts in Application event log