What was my Computer Uploading?

The internet in my house all of a sudden started going reaaaaly slow. I have iStatMenus installed on my computer so I can see what my computer is doing within the network.

The culprit for the slow internet was me! I had a 2MB/s upload speed... (my internet upload is capped at ~90kB/s when uploading anything to the internet - for example uploading files to dropbox) So I am pretty sure that I was uploading to something/someone within my network. I have a locked network and nobody in the house was doing anything so my worry is that someone else was on my network and was somehow accessing my computer. I restarted and after the restart my computer still started to upload at ridiculous food. I also force quit all the applications and iStatMenus did not show what application was uploading the data.

So my question is: Is there a way to find out what data my computer was uploading, or view an network log? I just want to make sure I wasn't uploading sensitive information. I am running Mavericks 10.9

Thanks.