So, I have been tasked with researching and deploying some kind of network auditing software. All this really needs to do is be able to ping/TCP-connect-scan a handful of internal /24 networks at regular intervals (every 24h or whatever) and send out an email if a new host is discovered or if a previously-existing host has gone away. Silly-simple to implement via Perl hackery, but Bossman wants a Shiny Web Interface(tm) and doesn't really want to pay for it. I've played around a bit with Zenoss, but that seems like using a sledgehammer to swat a housefly. Do you folks know of any software that can do that? Preferably this would run on a linux box, but I'm not going to be overly-picky at this point...
Many thanks!
The easiest way to do this is using something similar to Arpwatch
Most network reporting software can do this kind of autodetection, so it's really a matter of finding something that fits your requirements. You mentioned ZenOSS being too heavy, and that's fair, but for this kind of thing you'll generally be looking at some sort of network monitoring framework.
I know that Zabbix can also do this kind of probing and detection, and it's reasonably lightweight if you don't configure all the extra bits. It may not be ideal, but it'll certainly work.
It sounds like nmap-diff does most of what you need. You'd have to convert its output to HTML but that's trivial if you're comfortable with Perl. :)
You can also try The Dude