Yes.
Go to Message-->Create Rule From Message.
Under the first 1.Select a Condititon for your rule: check the box you need. (in your case you need to check the box for "Where the from line contains people") and go to third window 3.Rule Description. Here you see
contains
and when you click on it Select People window pops up. Click on Address Book and choose all the contacts in the adress book and move them to Rule Addresses (ie to the right side). Click ok. and then again ok.
Then from the second window 2.Select the actions for your rule: check the box with a text: "Flag it".
Click ok to close the window.
Hope Helps.