1 MD5 Cracking One way hash. Used in online passwords and file verification.

2 Lets destroy an MD5 hash Lets use “steiner” Md5('steiner')= 7bfd4d773bec1249bb691bbad9d968a8 Input into rcrack../rcrack *.rt -h 7bfd4d773bec1249bb691bbad9d968a8 Wait

3 MD5 hashing Tables vary greatly in size. Each added character add's exponential growth md5_loweralpha-numeric_ GB

4 General Wireless Vulnerabilities Invasion and resource stealing Traffic redirection Denial of service Rogue access points

5 The Wired Equivalent Privacy Protocol

6 Goals Confidentiality Prevent casual eavesdropping Access control Protect access to network infrastructure Data integrity Prevent tampering with transmitted messages

7 Logistics A key is shared between the client and access point Key length is 40 bits or 104 bits Keys are static and whenever a key changes, all clients must update

8 RC4 Stream Cipher

9 WEP Implementation of RC4 Checksum of the plain text is computed to provide data integrity 24 bit Initialization vector (IV) is used to increase the size of the secret key IV also makes it harder to crack by changing the key stream every time IV is pre-pended to the cipher text, that way client can decrypt the message

10 Encryption Process

11 Decryption Process

12 WEP Authentication Client sends message to access point (AP) requesting authentication AP sends plain text stream to client Client chooses IV and encrypts plain text stream Client sends IV and cipher text to AP for verification

13 WEP Frame

14 WEP Flaws and Exploits

15 Database Attack Some access points allow traffic to be encrypted or unencrypted Hacker sends packets to the access point broadcast messages, AP responds with encrypted version Hacker records key stream and puts it in database for later use When client gets sent message with IV that is in the database, hacker XORs the two to get the plain text

16 Key Scheduling Attack Some IVs are weak and through statistical analysis can reveal information about the key Active attack involves de-authenticating client repeatedly until enough packets have been received to analyze Utilizes the fact that several bytes of IP traffic can be easily predicted

17 Message Injection Hacker can listen to authentication process and determine a key stream for a particular IV Using this key stream, hacker can create packets and inject them into the network WEP allows for IVs to be reused without triggering an alarm

18 WEP Cracking Tools

19 Linux Security Distributions Several live CDs are available that contain all tools necessary to hack WEP Common applications include: Aircrack Suite - wesside-ng - aireplay-ng - aircrack-ng Airsnort Kismet

20 How to Protect Against and Attack

21 Newer Security Protocols Stop using WEP and use a newer protocol like WPA Make you password harder to crack by using the maximum number of characters and using random ASCII characters ***(deprecated)***

22 Authentication Evil Twin Attack Hacker can force user off the AP, then use the same SSID to pose as the AP How do you know who has control of an access point? Enterprise systems can use a server to authenticate users

23 Other Suggestions Wireless IDS Can monitor network to prevent rogue access points If attacker attempts to break into wireless LAN, the IDS can triangulate his location Use end to end encryption VPNs

24 Demo Locate target Do research Get AP MAC and client MAC Input into wesside-ng If necessary, spoof a clients MAC

25 Lan Manager (LM) Hashes Used by Microsoft Windows passwords are stored using this algorithm Only hashes 7 characters at a time. Makes cracking considerably easier

26 Lets break my windows Get Hash Input into ophcrack wait