I got my TI-99/4 confiscated by law enforcement when, after watching War Games, I wrote a script to "war dial" connection strings on the local Tymnet POP. Turns out one of the systems I connected to was the backend clearing system for Credit Suisse. They were neither happy nor had a sense of humor. After logs showed I didn't try to steal money or do anything damaging I got my computer back in a couple of weeks.

A couple of takeaways:

a. Credit Suisse did not have a username / password to log in. They were using "security by obscurity" in 1980.

b. The local FBI guys in Dallas didn't know you could purchase a modem for a couple hundred bux and hook it up to a $1000 personal computer. They seemed truly surprised to discover I wasn't part of a well-funded white collar crime syndicate and just a kid in jr. high school whose parents eventually gave in when I begged for a modem for a couple months.

c. You can apparently do damage to your reputation at 300 baud.

In the early 90's I worked for Louisiana State University's AG Center purchasing department and had a mainframe TSO account. I figured out how to use Gopher to various other research universities and download weather satellite photos and other various weather data (sometihng I was interested in at the time). I was then able to subsequently use Zmodem downloads over a 3270 dial up session to do this from home. I thought being able to get this info was pure magic at the time, since it was primarly only available to researchers.

My supervisor got the next month's TSO departmental chargeback bill for my user account from the University's IT group, and it was tens of thousands of dollars of TSO time :). They told me "don't do that anymore"