Linux Server Security + PLESK

Hi, I have my domain hosted with 1and1 hosting services based on a linux server. Overnight everyday I have a CPU overload which cause my emails stop working normally, this cause instability and recurrent issue. I guess my server has been compromised. I need a Linux security expert to get my server logs, identify the issue and secure my server for these issues not to happen again. I will need to receive the explanation of the issue and the corrective proposals before implementing them. s16322141:~ # ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10 %CPU PID USER COMMAND 0.5 993 postfix ./[login to view URL] -f -P /var/run/ctmilter/ctmilter -u postfix -G -d MISC -s -I -p /var/spool/postfix/ctmilter/[login to view URL] -O --ctasd-outbound-port 8088 -f 0.5 25758 psaadm /usr/bin/sw-engine-cgi -c /usr/local/psa/admin/conf/[login to view URL] -d auto_prepend_file=[login to view URL] -u psaadm 0.4 26177 root -bash 0.4 25760 psaadm /usr/bin/sw-engine-cgi -c /usr/local/psa/admin/conf/[login to view URL] -d auto_prepend_file=[login to view URL] -u psaadm 0.4 25759 psaadm /usr/bin/sw-engine-cgi -c /usr/local/psa/admin/conf/[login to view URL] -d auto_prepend_file=[login to view URL] -u psaadm 0.2 26171 root sshd: root@pts/0 0.1 1108 popuser spamd child 0.0 9 root [kworker/1:0] 0.0 988 root [kconservative]