an article on packet sniffing. this should be a reminder, unless you’re using SSL (HTTPS), or you’re tunneling traffic through an SSH connection, your data is not secure
Packet Sniffing on Mac OS X with Wireshark – dylanedwards.com.
[update] – turns out, the software linked to (wireshark) is prone to its own security holes: http://wiki.wireshark.org/Security