Using Standard Deviation to track SSH traffic

[serwin]

I'm looking for a way to traffic the average ssh traffic between two IP addresses (source IP and destination IP) and hopefully find when a host is doing more SSH traffic than usual and alert on it. I've been looking through some of the standard deviation paperwork and I think I found a search I wanted to do but the standard deviation I get is zero; which doesn't make sense.

Here is what I've been playing around with.

sourcetype="cisco:asa" dest_port=22
| stats count by src_ip, dest_ip 
| stats mean(count) as mean, stdev(count) AS stdev by src_ip 
| eval stdv_percentage=(mean/stdev)*100

[clara-fication]

have you looked through this? http://docs.splunk.com/Documentation/SplunkCloud/6.6.3/Search/Findingandremovingoutliers
you might want to use IQR, instead of standard dev, but it depends on the data and what works best.

try something like this:

sourcetype="cisco:asa" dest_port=22 
| stats count by src_ip, dest_ip 
| eventstats avg(count) as avg stdev(count) as stdev by src_ip
| eval lower_bound=avg-(stdev*2)
| eval upper_bound=avg+(stdev*2)
| eval isOutlier=if(count>upper_bound OR count<lower_bound,10,0)