DDOS attack from my Server IP [duplicate]

DDOS attack from my Server IP [duplicate]

This question already has an answer here:
How do I deal with a compromised server? 10 answers
hi guys I got warning from hosting provider for DDOS attack from my server
IP. I am new to Linux server admin, from traffic statics only 50mb inflow
data is noted on that day of attack, Do you think any script causing
DDOSing.. I configured Bind DNS, Apache , postfix , dovecot , Fail2Ban in
Centos 6.4 64 bit. Any security tips are welcomed..sorry for my English
:-p