How to Protect Webserver from different attacks

Hi All,

We need your advise to protect our webserver we have webserver installed on Windows server 2008 Ent SP2, we have installed following software for protection but we are facing problem every month our server goes down because of different hacker attacks (some strange bat files found in Windows/System32 folder and unknown users accounts created). so anyone can advise what we need to do for protection.

Windows up to date

Antivirus up to date

Internal Firewall is On with allowed specific port

External firewall

Regards

Agha