simple question on regex

I need to write a regex to match packets based on login id a_at_b.com. This
login id will be used to log in to yahoo messanger and I want to match this
login id regex in ASA inspection class.
What would be the right answer

1: "a_at_b.com"

or

2: "[aA]@[bB].[cC][oO][mM]

Thanks for your help.

Ajay

Blogs and organic groups at http://www.ccie.net
Received on Mon Mar 01 2010 - 15:49:55 ART