Seriously need help from someone who knows the WEB

I useally go on 4chan to check /b/ for some random funny stuff, then recently my computer started spamming me with *WARNING a hacker may be attempting to steal your data* is it possible that i got this from browsing 4chan? or do you think my room mate did this? he browses misc topics but i check the history and its some redtube witch one do you think could cause this?