By Mark Bowytz

SuperbNet was by no means a bad ISP. Opening during the 90’s, they offered a nice alternative to the 15 hours of "free" disks that arrived in the mailboxes of local residents. Their prices were competitive and service was very reliable. That is until one day, out of the blue, Jonathan’s Linux box would not connect to the Internet.

After firing up a terminal session, some troubleshooting revealed the culprit.

ppp0 Link encap:Point-Point Protocol
inet addr:10.0.0.1
P-t-P:XXX.XXX.XXX.
XXX Mask:255.255.255.0

For whatever reason, the ISP was giving him a local IP address of 10.0.0.1. Oddly enough, that was the same address of the Ethernet adaptor on Jonathan’s computer.

After adding the ‘noipdefault’ option to pppd-config (the dial-up networking configuration file), his network card and dial-up no longer butted heads, and everything was hunky dory again.

However, once connected, Jonathan’s mind was swirling with questions – Why was he suddenly allowed to change his IP address? Isn’t this a BIG security risk? What would happen if a computer's IP address was the set to the same as someone else's? Even worse, what if…

Jonathan froze for a second. Wouldn’t the ISP’s DNS server constitute “any” IP address?

He knew then that he just had to try out his theory and then got to work.

After some time, Jonathan managed to hack up a copy of a POP3 server so that it would log all connection attempts (and a SMTP proxy so that any outgoing mail would get forwarded on at a later time). Then, after cloning a copy of the ISP’s home page, his set up things so that all web requests would serve up the ISP’s homepage from his local Apache server.

Jonathan then updated his dial-up networking configuration and then “threw the switch” by connecting to his ISP. Suddenly, his poor 28.8kbps modem was flashing in “rave mode” trying to serve the needs of anybody connected to the ISP. Jonathan was floored when he noticed that after only 5 minutes, he had dozens of usernames and passwords.

Jonathan quickly disconnected his computer from the ISP and dialed up SuperbNet’s support line to report his findings.

“Hey, I think you have a problem with your service – I was able to spoof your DNS server by simply changing my dial-up settings!”

Jonathan heard the technician click-clack on his keyboard “Yup, DNS server looks to be working. You should be fine – Are you on Windows 3.1 or 95?”

“Tell you what," Jonathan sighed, "let me just reconnect, and then call you back.”

After freeing up the phone line, Jonathan connected to the ISP and then walked to the local gas station to use their pay phone to call SuperbNet’s support line.

After 15 minutes of “Hmmm” and “That’s strange” from the other end of the phone, the support tech finally said “I think this is going to take a while – could you disconnect and well, just not do that thing you’re doing anymore? We’ll continue to investigate though – thanks for the tip!”

Jonathan agreed and, as he hung up, he wondered if he could find a way to get the service from the "15 FREE hours" company to work in Linux.

Years later, and long after switching ISPs and mostly forgetting about "the incident", Jonathan was at a friend's house and needed to access the Internet. While dialing up, he noticed that his friend was using SuperbNet so, out of curiosity, he edited the properties of the Windows 98 dialup connection to use a static IP address. And lo and behold, SuperbNet dutifully assigned him the requested IP address.

Fortunately, SuperbNet never quite made it past dial-up, and as a result, their customers were acquired by a national conglomerate and eventually converted to DSL.