The tool looks as ad banner that can automatically appear by opening some internet resources, in case of “Close” button clicking ad banner will be opened in a new browser tab.
PopUnder is an ad window that appears by performing any action on a website. PopUnder ads are similar to pop-up ads, but the ad window appears hidden behind the main browser window rather than superimposed in front of it. A PopUnder windows are mostly displayed in front of webpage. PopUnder window is mostly created with Java Script and Cross-Site Scripting , sometimes using Adobe Flash but also can be generated otherways.