Recently, my MacBook Pro (early 2011 model, running OS 10.8.3) started becoming quite hot after only about three minutes of normal usage that didn’t involve running any computing intensive applications. Consequently, the fan would run at its maximum and the battery would quickly drain.
Initially, I did an SMC (System Management Controller) reset but that didn’t solve the problem. The next step was opening of the back lid and removal of accumulated dust from inside, particularly from the fan. Cleaning the fan resulted in a marked improvement but still the machine was running much hotter than normal without any apparent reason.
It then occurred to me (quite late!) that there might be some background process overloading the CPU. Checking the Activity Monitor confirmed this - process ‘parentalcontrolsd’ was taking up to 90% of CPU! Killing the process was ineffective as it would restart automatically.
I had never enabled Parental Control for any user account on this Mac; however, the Guest account has the parental controls enabled by default which was resulting in the running of the problematic process. Disabling parental controls for the Guest account from the System Preferences, finally, solved the problem!
It was interesting (or rather frustrating, depending on the perspective) to find that Mac users on Apple Support forums had complained of high CPU usage of paranetalcontrolsd and the resulting problems way back in 2007! After almost half a decade, the problem still persists!
Note: Users in the Apple Support forums suggest removing the folder Library/Application Support/Apple/ParentalControls, restarting Mac and enabling parental control again.