Solaris + viruses

UNIX Solaris
1

I know that UNIX is almost untouchable but my server is slower than previous days .
I found out that some users have watched porn on net , could they compromised system security .

So I have 2 questions

  1. Has on market any viruses for Solaris

  2. How to block some internet sites under Solaris

2

2 answers, recommended patches and use of firewall