That can really be annoying.  It has happened to me, too.  Now I unplug my cable modem and close, not just disable, my antivirus/security software.  Now I know I am safe from those updates and have more resources available.  Leave a post-it on your keyboard to remind you to turn the security stuff back on!! 
I also like to run long renders after a fresh restart so I know there are no pesky updates for JAVA or Adobe that have been hiding.  They usually run when the computer starts up.

Good luck.