I was a student there 1986-1990, then worked full-time on Athena until February, 1998. What you say has been true a long time. There are no-trespassing signs

I was a student there 1986-1990, then worked full-time on Athena until February, 1998. What you say has been true a long time. There are no-trespassing signs at all MIT entrances only so that the MIT police can legally eject people who cause trouble. Casual visiting is normal. In 1994 I pushed hard to get kerberos-authenticated telnet into the Athena release. The general sentiment from others was that, sure, sniffing passwords was possible, but distributed computing was advancing to the point where people would be able to do everything from their desks, and wouldn't need remote logins. So kerberizing other services was a higher priority.