Malware? ib.adnxs?

Hey everyone,

So as I am browsing the web, I noticed that my Air was being slower. I went to look into my history and noticed all of the sites say something along the lines of "ib.adnxs". It seems to be some type of malware or popup.

Has anyone ever had this before? If so, how do I get ride of it? Also, what exactly is it?

Thanks!