WLAN Information Security
Workshop on Wireless
Belgrade - 12.09.2011
Wenche Backman-Kamila
CSC – Tieteen tietotekniikan keskus Oy
CSC – IT Center for Science Ltd.
Let’s clean up the mess!
WPA2
webauthentication
Agenda
• The physical interface
• Authentication
• Encryption
• Traffic management
• Recommendations and comments
The physical interface
• Licence-free frequency bands
– 2,4 – 2,5 GHz (802.11b/g/n)
– 5,2 – 5,7 GHz (802.11a/n)
• Threaths
– Interference from
• Microwave owens and motion sensors
• Bluetooth, other wireless equipment, other WLANs
• RF jammers
– DoS attacks (assosiation or EAPOL Start)
AUTHENTICATION
Overall security of
authentication methods
802.1x networks alternatives
• 802.1x networks = eduroam networks
• 802.1x based on EAP
• EAP alternatives
– TLS
• Requires personal certificates but no username
and password
– TTLS, PEAP and FAST
• Authentication based on username and password
Supplicant configuration
considerations
• For 802.1x to be really secure pay
attention to which server certificate is used
• In the supplicant
– Define correct CA
– Define server name
• More info in WLAN monitoring and
supplicants - session
Information security risks in
web-authentication
• The authenticity of the login page cannot
be verified
• User IDs and passwords can be
intercepted and sessions hijacked.
Authentication
considerations
• Content of database
– Eliminate authentication with shared user
identities
• Impact of compromised credentials
ENCRYPTION
Wireless security vs wired
security
• Signals from Access Points can be
captured at the air interface
• Information security risks
– Sniffing
– Spoofing
– Probing
More security risks – and
countermeasures
• Firesheep
– Users may get their profiles to e.g. Facebook
hijacked
• Countermeasures
– VPN encryption
• High requirements on the VPN server
• Performance usually drops
– ->Link-layer encryption
Overview of encryption
development
Personal and Enterprise
• WPA-Personal WPA2-Personal (=WPAPSK WPA2-PSK)
• WPA-Enterprise WPA2-Enterprise
(=802.1x)
Details on WPA-TKIP and
WPA2-AES
WPA-TKIP
• regular key rotation
• per-frame key mixing
• a frame sequence
counter to protect against
replay attacks
• an improved message
integrity check algorithm.
WPA2-AES
• Actually AES-CCMP at
link layer
• A single component
handles
– per-frame key management
– integrity checks
TKIP-vulnerability
• End of 2008
– Injecting false messages of a few types (e.g.
ARP) possible
• September 2009
– Forging short encypted packes (e.g. ARP
messages) in shorter time (1 min vs 12 min)
– Increased likelihood of session being hijacked
• Although encryption key never exposed
– -> use only WPA2-AES
Wi-Fi alliance and WPATKIP
• Wi-Fi alliance will abandon WPA-TKIP in
stages 2011-2014.
Encryption conclusions
• Always use the most secure encryption
method WPA2-AES
• Why?
– When all use the same method roaming
becomes easier
– The Wi-Fi alliance is discontinuing support of
WPA-TKIP
• For access to intranets etc. include also
VPN encryption
TRAFFIC MANAGEMENT
Authorisation
• Minimum requirement is Internet access
• Separate VLAN for own users and visitors
– @myorganisation more rights and privilegies
• Check visitor VLAN carefully
– no protected networks or machines using the
same VLAN
• If possible access to printers and journals
for all
MAC address blacklisting
• Information security and stability can be
improved
– by stopping
• Too frequent authentication requests
• Spreading a worm
• constantly receiving new IP-addresses
– by handling notifications of copyright
violations
• The user should be notified of blacklisting
Other restrictions
• SMTP
– Only access to own servers allowed
– Block connections from the Internet
• Block devices from acting as DHCP
servers
• Make terminals communicate with each
other through the AP
RECOMMENDATIONS
Regarding authentication
• Inform of the weaknesses of unencrypted
networks
– and of the need to switch to 802.1x
• Consider implications of stolen passwords
• Or use different passwords for WLAN
• Grant access to VPN without webauthentication
• Don’t allow use of unencrypted protocols
in unencrypted networks
Comments regarding
authentication
• Open networks are misused and
copywright infringements occur
• MAC address blacklisting improves
security and stability
Regarding encryption
• Use only WPA2-AES
– If you have VERY good reasons allow also
WPA-TKIP
– Acknowledge supplicant configuration
implications
• Unencrypted networks are risky
– Open networks
– Pre-shared key networks
– Web-authenticated networks
References and contact
info
• Main reference
– WLAN Information Security BPD
• http://www.terena.org/campus-bp/bpd.html
• Wenche.Backman-Kamila@csc.fi