IN THIS CHAPTER
Finding security holes on your network with Nessus
Locating potential vulnerabilities with Saint
Testing known exploits on your network with Metasploit
Network scanning, covered in Chapter 20, lets you determine what someone could learn about the Macs on your network at a relatively high level — such as their IP addresses and what ports are open. That's extremely useful information and can provide important clues to blocking security risks. However, there's another side of the equation, which is what software is running on a particular Mac, at a particular IP address, and listening on a particular port.
For example, the fact that a device with IP address 22.214.171.124 is listening on port 9100 doesn't, by itself, tell you whether it's at any risk. What matters is whether the software that's listening for incoming traffic on that port is subject to any specific attacks. It so happens that port 9100, my randomly chosen example, is mainly used by certain kinds of printers, so the biggest risk one might face with having that port open to the outside world is that someone outside your network may try to print something on your printer — potentially annoying but hardly a big deal. On the other hand, if the device in question is a Mac and if the software listening on a particular open port is outdated or faulty, it could open your Mac to all sorts of trouble, including being taken over remotely and having all its data stolen! ...