The IP Logging feature may be what you are looking for. The IDS can be set up to take an action of log for any signature event. This will cause the sensor to log all packets that are transmitted or received by the suspect attacking host from the point of an alarm on.
The sensor can also be set up to log all traffic from or to any given host as a matter of course, however this will have a negative impact on the perfromance of the sensor due to the overhead of writing packets to the disk.
