We had a case when one of the customers complained of being blacklisted because his whm server was sending spam. We had to act fast in order to stop this. We did the following.
It very important to have clear understanding and reference to location of your cPanel VPS log files. This is the case in case of web attacks , security relayed issues or just good old troubleshooting. This is very basic overview of all log files used by cPanel and where they are locate.