Network Security – so https and ssh are immune to arp spoofing right?

When a machine has been arp spoofed, ALL network traffic from it is likely passing through a “hostile” machine. So, NO, https and ssh traffic is not immune, it is travelling through a hostile machine. However, it should be encrypted. There are a few exceptions though. SSH version 1 is a broken encryption scheme and should be avoided like the plague. As far as I know SSH 2 should be safe. Pay attention to complaints about the host identification not being able to be verified….

HTTPS is also an encrypted protocol, usually used for online banking logins, etc. There is a problem though…. one of the responsibilities of certificate based authentication is that the end user has the ultimate call if a certificate doesn’t match. (You do look at those right?)… SO…. it’s possible that an ARP spoofing attacker machine decrypts the network data from the https:// protected website and then generates a forged certificate and a new encrypted stream to the client machine.

The client machine at this point will complain and say something along the lines that the certificate could not be verified do you still want to accept? So, if the end user supports the forged certificate, then all https passwords can be sniffed as well, because they’ve accepted a fake certificate. So the moral of this story is to be extremely cautious when accepting dubious certificates. HTTPS can be secure, but ultimately it’s up to the end user whether or not they accept a forged certificate.

So what hope is there against arp spoofing?

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