I got an innocent question last week. We’d been scanning an AIX server with Nexpose, a vulnerability scanner made by Rapid7, and ran into some issues. The system owner then asked a question: The server is behind a firewall and has no direct connection to the Internet and no data itself, it’s just a front-end to two other servers. Is there any reason to scan a server like that?
In my sysadmin days, I asked a similar question. Nobody could give me an answer that was any better than “because reasons.” So I’ll answer the question and give the reasons.

David Farquhar is a computer security professional, entrepreneur, and author. He has written professionally about computers since 1991, so he was writing about retro computers when they were still new. He has been working in IT professionally since 1994 and has specialized in vulnerability management since 2013. He holds Security+ and CISSP certifications. Today he blogs five times a week, mostly about retro computers and retro gaming covering the time period from 1975 to 2000.
