CSC – Tieteen tietotekniikan keskus Oy CSC – IT Center for Science Ltd. WLAN Information Security Workshop on Wireless Belgrade Wenche Backman-Kamila

802.1x AES WEP TKIP WPA WPA2 WPA- Personal WPA- Enterpise PSK Let’s clean up the mess! web- authentication

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 (=WPA- PSK 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 WPA- TKIP Wi-Fi alliance will abandon WPA-TKIP in stages

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 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 web- authentication 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