Transcript Wireless Network Security

Attack and Defense in Wireless
Networks
Presented by Aleksandr Doronin
Outline
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Wireless Networks and Security
Attacking and defending WEP
Attacking and defending WPA/WPA2
Common defense techniques
Summary
Wireless Networks and Security
1) What are Wireless Networks?
• A wireless network is the way that a computer is connected
to a router without a physical link.
2) Why do we need?
• Facilitates mobility – You can use lengthy wires instead, but
someone might trip over them.
3) Why security?
• Attacker may hack a victim’s personal computer and steal
private data or may perform some illegal activities or crimes
using the victim’s machine and ID. Also there's a possibility to
read wirelessly transferred data (by using sniffers)
Wireless Networks and Security
Three security approaches:
1. WEP (Wired Equivalent Privacy)
2. WPA (Wi-Fi Protected Access)
3. WPA2 (Wi-Fi Protected Access, Version 2)
WPA also has two generations named Enterprise and Personal.
WEP (Wired Equivalent Privacy)
• Encryption:
– 40 / 64 bits
– 104 / 128 bits
24 bits are used for IV (Initialization vector)
• Passphrase:
– Key 1-4
– Each WEP key can consist of the letters "A" through "F" and the
numbers "0" through "9". It should be 10 hex or 5 ASCII characters in
length for 40/64-bit encryption and 26 hex or 13 ASCII characters in
length for 104/128-bit encryption.
WPA/WPA2 Personal
• Encryption:
– TKIP
– AES
• Pre-Shared Key:
– A key of 8-63 characters
• Key Renewal:
– You can choose a Key Renewal period, which instructs the device how
often it should change encryption keys. The default is 3600 seconds
Attacking WEP
• iwconfig – a tool for configuring wireless adapters. You can
use this to ensure that your wireless adapter is in “monitor”
mode which is essential to sending fake ARP (Address
Resolution Protocol) requests to the target router
• macchanger – a tool that allows you to view and/or spoof
(fake) your MAC address
• airmon – a tool that can help you set your wireless adapter
into monitor mode (rfmon)
• airodump – a tool for capturing packets from a wireless router
(otherwise known as an AP)
• aireplay – a tool for forging ARP requests
• aircrack – a tool for decrypting WEP keys
How to defend when using WEP
• Use longer WEP encryption keys, which makes the data analysis task more
difficult. If your WLAN equipment supports 128-bit WEP keys.
• Change your WEP keys frequently. There are devices that support
"dynamic WEP" which is off the standard but allows different WEP keys to
be assigned to each user.
• Use a VPN for any protocol, including WEP, that may include sensitive
information.
• Implement a different technique for encrypting traffic, such as IPSec over
wireless. To do this, you will probably need to install IPsec software on
each wireless client, install an IPSec server in your wired network, and use
a VLAN to the access points to the IPSec server.
Attacking WPA
• macchanger – a tool that allows you to view and/or spoof
(fake) your MAC address
• airmon – a tool that can help you set your wireless adapter
into monitor mode (rfmon)
• airodump – a tool for capturing packets from a wireless router
(otherwise known as an AP)
• aireplay – a tool for forging ARP requests
― Capture WPA/WPA2 handshakes by forcing clients to reauthenticate
― Generate new Initialization Vectors
• aircrack – a tool for decrypting WEP keys (should be used with
dictionary)
How to defend when using WPA
• Passphrases – the only way to crack WPA is to sniff the
password PMK associated with the handshake authentication
process, and if this password is extremely complicated it will
be almost impossible to crack
• Passphrase Complexity – select a random passphrase that is
not made up of dictionary words. Select a complex passphrase
of a minimum of 20 characters in length and change it at
regular intervals
Common defense techniques
• Change router default user name and password
• Change the internal IP subnet if possible
• Change default name and hide broadcasting of the SSID
(Service Set Identifier)
• None of the attack methods are faster or effective when a
larger passphrase is used.
• Restrict access to your wireless network by filtering access
based on the MAC (Media Access Code) addresses
• Use Encryption
Summary
• Change all possible default router settings
• Use encryption (WPA/WPA2)
• Use long and complex keys/passphrases
Thank you!
References
• http://www.backtrack-linux.org/
• http://www.aircrack-ng.org/
• http://www.youtube.com/results?search_que
ry=cracking+WEP+and+WPA+with+backtrack&
oq=cracking+WEP+and+WPA+with+backtrack
&aq=f&aqi=&aql=1&gs_sm=e&gs_upl=1621l1
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