All our workstations at school had static, publicly routable IP addresses. I never got hacked, thankfully, but I still found out about the pervasive ssh bruteforcing fairly quickly. The brute-forcing bots apparently were rate limited to once per second. Since each failed attempt gets logged to disk, this resulted in a faint, periodic "grrrt" sound. It's hard to describe how incredibly annoying this was while sitting next to the machine; certainly annoying enough to figure out what was causing it :-)