Lynx/MSIE denial-of-service

[drwho () L0PHT COM (Doctor Who)]

Some people may think of this as simple or old hat, but I find it quite
surprising that this is possible.

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.

Netscape Navigator disallows access to port 19. This is probably the best,
easiest fix to this problem. Further work should be done to figure out
what other services could cause problems.

The CHARGEN service has other security implications and should be turned
off in normal system operation.

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