Many systems run a service called "chargen" on port 19. It simply generates a never-ending stream of characters. If an MSIE or Lynx user connects to a chargen, the browser will act as though viewing a file of infinite length. This has caused a modem connection to drop using MSIE, and slowed a Linux system using lynx to a crawl due to exhaustion of memory. Both processes were aborted before any further damage was caused. A URL such as http://localhost:19 could cause the "flooding" damage to a system running lynx and chargen to occur almost instantly, because the characters would of course come at a much higher speed. The CHARGEN service has other security implications and should be turned off in normal system operation. ----------------------------------------------------------------------------------------- You can also create a serios DOS attack when this is combined with a proxy server. Using the URL: http://some.proxy.host/http://some.host.on.the.local.lan:19/ can bring some machines to a screaming halt. ----------------------------------------------------------------------------------------- Even simple HTML can cause problems. This one is great with NT web client users: