German police have <A HREF="http://zdnet.com.com/2100-1106_2-5208655.html?tag=zdnn.alert">arrested an 18-year-old man</A> suspected of creating the Sasser computer worm, believed to be one of the Internet's costliest outbreaks of sabotage. Security experts said this could be the single biggest arrest yet in bringing down a virus-writing gang.