Proxy question

[Bart Silverstrim]

We are currently running Squid and SquidGuard on FreeBSD for  
monitoring/proxying web browsing activity at our workplace.  The  
problem is that some users figured out how to use a specific type of  
proxy to bypass protections...specifically, they're going through an  
https site.

Is it possible to run a proxy that can monitor https connections and  
block them if necessary?

-Bart