Here are details of this signature:
You will want to track by using captures where the packets with a source of 127.0.0.1 are coming from (using MAC addresses).
You can use the packet display command on the sensor as well.
If there are any layer 3 hops, you will again have to capture on that layer 3 device.
the ips logs for the attack is following..i used packet dispaly command on my senson but couldnt find any any mac address ...
addr: 127.0.0.1 locality=OUT
addr: 126.96.36.199 locality=OUT
os: idSource=unknown type=unknown relevance=relevant
riskRatingValue: 100 targetValueRating=medium attackRelevanceRating=relevant
protocol: IP protocol 0
You can try using the packet capture command and then copy of the captured file to an ftp server and view it using wiresark. here's the document on using the packet capture command and also explains how to copy the capture file for analysis: