Re: Wireless Scanning

[Joshua Wright <jwright () hasborg com>]

Jason T wrote:
> Just a comment on using a WEP cracking programs.  I heard from Keith
> Parsons who is an expert wireless teacher saying that WEP cracking in
> the wild today doesn't exist in most cases.

I suspect Parsons said this based on empirical evidence due to the 
difficulty he perceives in recovery WEP keys.  Since most attacks 
against WEP are passive or offline attacks, it's difficult to know if it 
is used frequently in practice.  More below.

> In early 2002 all vendors saw the weak IV as an attack.  So they
> changed the firmware to no longer support those weak IV's.  If you
> want to crack WEP it will most likely be on an AP that has a firmware
> version prior to 2002.

While it is true that tools like wep_attack and AirSnort rely on the now 
less-common IV values, more recent tools such as AirCrack and WEPlab are 
successful at recovering WEP keys even when common weak IV's are 
filtered.  I've been successful at recovering WEP keys with as few as 
75,000 IV's with AirCrack.

Moreover, there are other key-recovery attack methods as well, including 
dictionary attacks and attacks against the Neesus Datacom key generation 
algorithm.  Not to mention many other attacks against WEP to inject 
frames or decrypt traffic without the knowledge of the WEP key (ICV 
invalidation, IV collision/known plaintext recovery, etc.)

WEP is badly broken.  Even when deployed in a dynamic keying environment 
with short key durations, it is susceptible to many different attacks. 
I recommend steering away from WEP-based encryption wherever security is 
a concern.

-Josh
--
-Joshua Wright
jwright () hasborg com
http://home.jwu.edu/jwright/

pgpkey: http://home.jwu.edu/jwright/pgpkey.htm
fingerprint: FDA5 12FC F391 3740 E0AE BDB6 8FE2 FC0A D44B 4A73

Today I stumbled across the world's largest hotspot.  The SSID is "linksys".