Its not that easy my friend, VAC is integrated with Black Ops. Meaning steam only holds your games, account, friends, ext... VAC which is integrated into Black Ops you can't really do anything about it except going to your config_mp.cfg which is located in "C:\Program Files\Steam\steamapps\common\call of duty black ops\players" For 64Bit Users its in "C:\Program Files (x86)\Steam\steamapps\common\call of duty black ops\players"
Once You found config_mp.cfg open it with Notepad++ and look for "seta sv_vac" and if it looks like seta sv_vac "1" just replace the 1 with a 0
you can do the same thing for your single player.
I hope i helped you. Have a good one.