Bringing Down Millions of WordPress Sites
Back in 1999 when I was learning to code (PHP obviously), I was stoked to discover the mail() function. Up to that point I'd only been doing HTML and JavaScript coding so my newfound ability to send emails was a pretty big deal. I asked my friend what would happen if I put the mail call inside a while(true) statement. He said it would run until the server hit the 30 second timeout. I asked how many emails my server could send in 30 seconds but he didn't know. I decided to to find out, directing all the emails to my hotmail account. Little did I know, that my ISP & hosting provider had disabled the default 30-second timeout so the script kept running. A few hundred thousand emails later I was having second thoughts about my poorly planned experiment. The next day I got a phone call from my ISP. Turns out Microsoft perceived it as a DDOS attack and blocked all traffic from my ISP.  And so for a day basically no one in my city could access their Hotmail accounts or any other Microsoft properties.  Oops.