System Hacked from MySQL Insecurities

[Kalpin Erlangga Silaen <kalpin () solonet co id>]

Dear all,

several days ago, someone hacked my test box using the latest FreeBSD. 
He explained that he rooted my box because he knows my root mysql 
password. Is it possible to hack system via MySQL ? or he just tricked 
me and try hide his way ? I am using MySQL 4.0.18 for FreeBSD.
My details system:

OS: FreeBSD 5.1
MySQL version: 4.0.18
Port : 3306

I opened port 3306 from Internet, so people can use this if they have 
access/username to MySQL.

Thank you.

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Kalpin Erlangga Silaen
mailto: kalpin () solonet co id
URL: http://www.warningnews.com
YM: kalpinus
MSN: kalpinus
IRC: mesra.dal.net nick Kalpin