What is meant by promiscuous mode ?

[guna_1]

Hi,

what is meant by promiscuous mode of a network interface card ? Why it is always mentioned when discussing about snooping / sniffing ?

Thanks in advance for the replys

[Charles Harris · Accepted solution]

Setting a lan card to promisc mode loosly means it will listen to all lan traffic on it's lan, rather than dropping packets that are not destined for the server it is connected to. Which is why it is a pre-req. for snooping!

[guna_1]

Thanks charle for ur quick response...

will promisc mode NIC allow hacking ?

Why some application want the NIC must be in promisc mode ?

How we can check whether my NIC is in promisc mode or not , if it so , How can i change to non-promisc mode

Thanks & regards ,
Guna

[Nicolas Dumeige]

Hello,

Ethernet protocol broadcast packets to all, i.e. the destination appears on the header, and when a NIC read this information, it leave the packet - this is the default behaviour - but all NIC can see all packets.
Proscuous is used for network analysis or hacking.

Cheers

Nicolas

[Nicolas Dumeige]

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=594140

[Charles Harris]

Hello again.....

To answer your other questions...

Setting a NIC to promisc doesn't really increase the risk of hacking, although it could be used by a local user to 'see' other server's traffic (clear text password etc) when used in conjunction with packet analysis tools.

Most programs that require promisc mode do so to allow network analysis / packet capture etc. tcpdump & ethereal are two good examples and can be very handy for niggling network issue.

Cheers,

-=ChaZ=-

[shetty]

Hi,

Normally an Ethernet interface reads all address information and accepts follow-on packets only destined for itself, but when the interface is in promiscuous mode, it reads all information (sniffer), regardless of its destination.

If you want some detailed information , you can try at the below sites. It gives an idea.
1) www.tsl.state.tx.us/ld/pubs/compsecurity
/glossary.html

2) www.entivity.co.uk/devices/
ethernet_glossary.htm

Regards.
Shetty.