Trustworthy Wireless

1. Trustworthy Wireless Jeffrey Pang, Srinivasan SeshanBen Greenstein, Ramakrishna Gummadi, Tadayoshi Kohno, David Wetherall Why You Should Worry About Wireless Privacy Ubiquity of 802.11 Networks (typically < 100m) Cheap Radios, Monitoring Software Ubiquity of 802.11 Devices tcpdump 802.11 Access Points in Chicago What Your Wireless Traffic Says About You Can Your Wireless Traffic Identify You? Can Your Wireless Traffic Reveal Where You’ve Been? • Yes: MAC address = unique identifier • Previously proposed solution: Pseudonyms (change MAC address each session) • Pseudonyms are not enough! • Implicit identifiers remain (exposed characteristics of network traffic) • Yes: Laptops probe for network names you’ve connected to before • Network names (SSIDs) are often identifying (e.g., “CMU,” “IR Guest,” “Bob Home”) • Fundamental Problem: device discovery and pairing is not private Implicit Identifier Examples Example of Where You’ve Been Network destinations: web bookmarks, your email server, VPN server, etc. Wireless Network Names: networks you’ve visited before (e.g., your home) 802.11 Protocol Fields: wireless card implementation and configuration Packet Sizes: size of broadcast packets (NetBIOS, MS Office, mDNS, etc.) (1) Collect some wireless data… “Anonymized” SIGCOMM 2004 802.11 Trace Visible even with WPA,WEP encryption! “djw” = David J. Wetherall’s Home Network? (2) Lookup suspect SSID in a war driving database… Implicit Identifier Accuracy Example: 1 in 4 users identified >50% of the time with 0.1% false positives (3) Find suspect’s home using Google Maps! hotspot home corporation Typical Hotspot Best Practices