I like to periodically scan my server’s open ports from another box on my network. Just to make sure that nothing’s listening that I don’t intend to listen. So I fired up nmap on my mom’s windoze box and did a TCP scan of ports under 1024. After the first 15 ports, the server stopped responding. I couldn’t ssh into it, telnet into it, or talk to the SMTP or IMAP servers on it. I panicked, thinking that a port scan killed the server. Then I realized what happened: Portsentry tripped when it detected the port scan. I totally forgot that I run tools to deter port scans. All I had to do was pop onto the console and delete the IP address from Portsentry’s blocklist.
Sometimes I really am stupid.