Application layer firewalls have existed for at least 6 years.
Make that 15....
I suspect that claiming to that they existed farther back than 1990 would require careful debate about the functionality. Taking it at its most general: a boundary barrier service that mediated particular application exchanges between an "interior" Administrative Environment, versus the rest of the public network. One can reasonably argue than any such mediation has a security component to it. Therefore one could argue that firewall functionality was around at least 25 years ago -- there were a number of email boundary gateway mediating services by then -- and very probably back to 1973. (I just know that some MIT type is going to claim pre-1970, given the generality of the definition I offered.) d/ -- Dave Crocker Brandenburg InternetWorking +1.408.246.8253 dcrocker a t ... WE'VE MOVED to: www.bbiw.net