I've found that Nessus scanners, I'm working with the 4.4.* variety, can't seem to take the loads that they're famous for dishing out.
For instance, if you scan a full class B, you can expect quite a bit of packet love from Nessus to your devices.
But turn the tables on Nessus and it falls on its face.
Try logging in to the scanner very quickly
- Log in, via the XML-RPC API</li>
- Request the list of plugins</li>
- Log in again via the XML-RPC API</li>
- Request the description of a plugin</li>
- Repeat steps 3 and 4 until Nessus goes tits up</li>
Enjoy your 100% CPU utilization and locked up nessusd.
I don't know why it works, but I suspect it has something to do with all the logging-in that occurs. Nessus may be leaving some connection open or something. The important part is that you want to loop really fast between logins. In my sample scripts I omitted the subsequent logout call but, let's be honest, any software that wants to be enterprise-y should be able to handle an assumed logout.