I've got a home network consisting of three machines connected through a wireless router which is connected to a DSL modem.

My Linux (FC3) system is a desktop connected directly to the wireless router (i.e., it's not wireless).

Is there an application on the Linux system that will allow me to monitor all of the traffic going through that DSL modem in both directions - a "packet sniffer" or something similar? If not, is there something I can download that will enable me to do what I want?

I mainly want to capture the text coming and going. For example, if somebody was using an instant messenger application on one of the Windows laptops I'd like to see the text messages going through my modem.

I did a search before posting this but didn't find anything useful.

Thanks.

Hi lyonsd,

ethereal should be in RH9, it does the trick. If you merely want to monitor where your darlings are surfing the net, etherape gives a good overview.

Keep in mind that your NIC must support "promiscuous mode", means, forward packages to the OS that are not meant to be for its MAC address - most cards do so on Linux, but don't tell me I have not told you

Keep in mind, monitoring a Person's network usage breaks their privacy, so be sure to announce to your users that you are monitoring and check if your local laws allow you to.

HTH, Peter
P.S.: Of course, you cannot monitor traffic that is kept away from you by a switch - for true monitoring, use a hub instead, because switches redirect the traffic to a specific NIC's MAC only to the switch port the NIC is connected to, and not to the other Switch ports!
P.P.S: Glossary: NIC = Network Interface Connector, the Ethernet card; MAC = Media Access Code, the hardware-given Ethernet Address identifying the NIC.

I have Fedora 3, so I'll check and see if etheral/etherape is there and if it works or not.

I hope either of these can capture instant messenger messages.