Can attackers harvest WiFi passwords by spoofing ESSID?

Question

I've recently started using wireless on an (Arch) laptop. My wireless manager (wicd) is set up to automatically associate with any networks with a certain ESSID and attempt to authenticate with them.

Is that a security risk? In particular, could an attacker set up a network with the same ESSID as the one I connect to, then wait for my wireless manager to try to connect, and receive my authentication details?

edit: The network I am connecting to uses WPA Enterprise authentication which requires an identity and password, not an encryption key.

Answer 1

Pre-shared-keys are never transmitted during the establishment of a wifi session - in other words the client never says "This is the key I have, can I come in?".

Simplifying what happens somewhat in a crappy WEP session, it goes like this:

1. The client says "I'd like to authenticate"
2. The access point says "Ok, use your key to encrypt this data", sending some random data
3. The client encrypts the data with the key and sends it back
4. The access point checks the encrypted data matches its own version of the data if it encrypts with the key, and lets them in if it matches.

A rogue access point is a security concern, but not one that will make harvesting keys any easier than simply watching the above interaction. The real concern is that people will connect to a rogue access point and transmit sensitive data over it thinking it is an authorised AP.

Answer 2

As stated by Paul, this is not possible. For the best home safety just use WPA2. It is easy to set up and protects pretty good. One thing you might want to consider is using a non logical password. If you use "sittinginthesun" as a password it is easily cracked by a dictionary attack while "347asdxjaser8q348szd" is way harder to crack, because the key is not logical and brute forcing doesn't work that well on WPA. For WEP this doesn't work.

I tried cracking my WiFi connection which is set up with a PSK of 26 hexadecimal numbers and letters. WEP was cracked within a few minutes, WPA took me a lot longer and WPA2 wasn't cracked, only when i used "sittinginthesun".