Cisco Firewall :: ASA 5505 Using Logging & Packet-capture To Locate Virus Infected PC

ATT notified my company we have a virus infected pc on one our networks which sits behind a Cisco ASA 5505 running 7.2(4). The set up is a basic inside/outside NAT configuration. They gave us the destination ip address and port which the our pc is contacting.  I have been tasked to track down the infected pc.  I created the following access-list and applied to the inside interface:
 
access-list VIRUS extended permit TCP ANY host x.x.x.x EQ YYYYY log debugging interval 600 access-group VIRUS in interface inside
 
I enable logging to the console whose output did not list the IP address of the infected pc, only the ip address of the DNS servers we were using. I then used the following capture commands to try locate the internal ip address of the infected pc:
 
capture in-cap interface inside access-list VIRUS-CAP buffer 1000000 packet 1522 capture in-cap access-list VIRUS-CAP interface inside
 
Neither step worked and the resulting console output overwhelmed the firewall in a very short period of time. Before attempting this task again, I would like to know if I am going about this the right way or if there is a better methodology?