>My employer has asked that I block access to instant messenger services
>like ICQ, MS Messenger, AIM, and YIM. I know ICQ used port 4000 at one
>time, is that still the case? What ports do these other services use?
>Any help would be appreciated. I checked IANA's well-known port list,
>but it wasn't much help - doesn't list any specific service except ICQ,
>which conflicts with another previously-registered service (which is why
>I was wondering if it changed).

it sounds to me like there are random services you don't want to pass
through your packet filter.  perhaps it might be easier to allow only
those services you know you need?  that way you can be sure to block
the random outbound connections to gnutella and gnapter like networks,
random instant messaging services, etc.  the usual sorts of things
that people like to block.  anything that's being legitimately used
will probably have a specific for associated with it.

-- 
|-----< "CODE WARRIOR" >-----|
codewarrior@daemon.org             * "ah!  i see you have the internet
twofsonet@graffiti.com (Andrew Brown)                that goes *ping*!"
andrew@crossbar.com       * "information is power -- share the wealth."