Trustworthy Wireless

Trustworthy Wireless

• 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)

Can Your Wireless Traffic Reveal Where You’ve Been?

What Your Wireless Traffic Says About You

(typically < 100m)

Cheap Radios,MonitoringSoftware

Ubiquity of802.11

Networks

802.11 Access Points in Chicago

tcpdump

Can Your Wireless Traffic Identify You?

Implicit Identifier Examples

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.)

Implicit Identifier Accuracy

Typical Hotspot Best Practices

Example: 1 in 4 users identified >50% of the time with 0.1% false positives

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• 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

Example of Where You’ve Been

“djw” = David J. Wetherall’s Home Network?

(1) Collect some wireless data… “Anonymized” SIGCOMM 2004 802.11 Trace

(2) Lookup suspect SSID in a war driving database…

(3) Find suspect’s home using Google Maps!

Jeffrey Pang, Srinivasan SeshanBen Greenstein, Ramakrishna Gummadi, Tadayoshi Kohno, David Wetherall

Ubiquity of802.11

Devices

Why You Should Worry About Wireless Privacy

hotspot home corporation