Seoul - South Korea's Daum Communications announced on Wednesday that it has signed an agreement with Google to use the company's AdSense system to serve search ads on its Internet portal. Daum claims 38 million registered users, and collects more than one-third of its revenues from online advertising. The company also owns Lycos, which it acquired from Terra in 2004, but has recently fallen into second place among Korean portals behind NHN Corp.