best monitoring/keylogging software

[objc]

I am having a problem at work where someone (the janitorial staff?) is coming in and using the computers in my office without permission. I'd like to install some monitoring software to see who's doing it and what they are doing. I'd appreciate some recommendations. TIA.

 

[SilentPanda]

A very similar thread was made about this yesterday. Please use the search function. Thanks!