It's your network (presumably) ”shouldn't you know what's going on? This chapter introduced several sniffing and portscanning tools that can be used to audit your network security, help detect inappropriate use of your network resources, and even uncover others using similar tools against you. The tcpdump utility is part of Mac OS X and can easily display all packet activity on your network. The ettercap sniffer, on the other hand, provides attacker-style features including password filters, ARP poisoning , and more. Finally, portscan tools such as NMAP can help an administrator (or an attacker) map out vulnerable systems on their network by identifying active services and OS versions.