512MB RAM aren't good.
1)apache2: noes, if any small attack shows up it'll crash in seconds.
-> Switch to lighty & FastCGI PHP, uses less ressources and serves the visitor faster.
2)Way too many open ports/running services (just a few listed below)
21/tcp open ftp
25/tcp open smtp
53/tcp open domain
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
465/tcp closed smtps
993/tcp open imaps
995/tcp open pop3s
If one of these services gets fucked by a single 0day, the whole server is.
3)Use CloudFlare.com
->Cause it's awesome!
TL; DR
Nearly perfect job Panki & ThePro, my guess is that you installed the standart CentOS-Kloxo image on tha box tho
mhm...CentOS.... :megusta: