A research paper released by a U.S.-based security expert last week highlighted the weaknesses of the new Wi-Fi Protected Access (WPA) standard compared to its predecessor, wired equivalent piracy (WEP) – the most commonly used wireless security standard.
According to Robert Moskowitz, senior technical director with ICAS Labs, a division of TruSecure Corp., his paper entitled Weakness in Passphrase Choice in WPA Interface centres around weaknesses found in pre-shared keys (PSKs).
PSKs – which are not found in WEP – make it possible for wireless network attackers to easily determine the passphrase an organization is using to protect its network.
The WPA standard, which is based on the 802.11i wireless security standard, can be deployed by authenticating remote users to a network through the 802.1x protocol, which talks back to a back-end security server, usually a radius server.
Moskowitz said that because of the complexity of this model, this WPA deployment method would be most popular in medium- and large-sized organizations.
PSKs entered the picture because the 802.1x protocol is difficult to set up and requires a back-end server but “the vendors insisted on a simpler method for small offices and home installations…a pre-shared key.”
Although smaller organizations may not understand the need for this kind of security, Moskowitz said it is imperative for any company using a wireless network.
“You say, ‘well gee, who is going to listen to my network? I have a small business.’ What about the office building next door that is struggling, when they [realize] they can save $100 a month by dropping their Internet connection by just tapping into the guy next to them?” Moskowitz said.
Although the PSK method is simpler to deploy and set up, Moskowitz said users have to use “good secrets” when choosing a passphrase or the wireless network won’t remain secure. He added that PSKs can range from eight to 63 bytes and PSKs less than 20 characters long are unlikely to withstand an attack.
If a “weak secret” is used in a PSK, it is relatively easy to determine that secret through an offline dictionary attack, he added. A dictionary attack is when an attacker, by hand or through software, uses words from the dictionary to guess a user’s passphrase.
This is why Moskowitz said it is imperative to choose a long alphanumeric passphrase that can’t be found in a common dictionary.
“You don’t choose ‘roses are red’ or your mother’s maiden name, you have to choose a good one,” he added.
Moskowitz said that if companies are sharing passphrases with visitors, they must always remember to change the passphrase once the guest has left the building.
Organizations using WPA with PSKs should also consider using a random number generator to create passphrases, rather than making them up, Moskowitz added.
However, companies that are deploying WPA with an authentication server have little reason to be concerned because they do not use PSKs, according to Michael Disabato, senior analyst at the Burton Group Corp. For other WPA users, the Moskowitz paper should not cast a shadow over the standard, he said.
“WPA is doing what it’s supposed to do, providing you do what you’re supposed to do and enforce secure passwords.”
Other problems make the job of compromising such networks easier, Moskowitz said. Included in those issues: meeting the requirements for some wireless products, and that all wireless users share the same PSK on a network.
Moskowitz’s report is circulating informally on the Internet, but an official copy will soon be available on the TruSecure Web site at www.trusecure.com.
– With files from IDG News Service
