Our all file infected by malicious codes

[sommart]

Hi all, our forum got DDoS Attack by someone and our account suspended by hosting company. and they are saying that your all mybb file have malicious codes. then i have changed other hosting company but same problem and saying your mybb files compromised. how to check malicious codes? if i'll install fresh mybb then i can restored database? or also database affected?
Please help. thank you

I have installed:
Mybb version 1.6.10
Announcement plugin
Antiproxy plugin
google seo plugin
plugin uploader
pm log plugin
ChangUonDyU - Advanced Statistics 1.0.1
and chatbox plugin