A sadly common pop-up advert models itself on the default Microsoft Windows™ alert messages, with the message “Your computer is broadcasting your IP over the Internet”, in a sad attempt to get gullible people to mistakenly click “OK” thinking it’s a genuine alert. Clicking “OK”, or indeed anywhere within the advert, presumably takes you to some horrible fake-Viagra site or something similar.
See also: Costello’s reward for being loyal (Costello)