Could be a number of things including mods if you have any pulling data. Could just be ray, or a refresh of a module or anything really. I have seen this in the lower left in firefox on a number of occasions but it really hasn't result in any significant bandwidth of any kind.
Depending on the browser and site, some times I see this and sometimes not.
Is there some issue you are concerned about in regards to this? If it is chewing up bandwidth maybe something to explore, or if something is accessing a connection, site or info that might cause alarm or further investigation maybe. Otherwise I do see this fairly often and never spent a lot of time on tracking it down.