The convars that psychedelic posted are nothing but the server outputting information to all clients currently connected. You cannot see the commands players enter into their console. That is only viewable to the server console. You only see the server information in your console as well as YOUR client information.

The only way to crash CS:S servers nowadays is with a proper DDoS unless owners open themselves up to vulnerabilities. IBIS can handle most attacks. I don't believe they crashed the server directly.