Catching IMSI Catchers
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Read Geoffrey Vaughan's presentation of DSS ITSEC 2016 on how IMSI Catchers work, detection strategies, and how to avoid being caught up in one.
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Catching IMSI Catchers
- 2. What you will learn today 1. What IMSI Catchers do and how they work 2. Detection Strategies 3. Hear an exciting tale of adventures in Vegas 4. Learn how to avoid being caught up in an IMSI Catcher
- 3. Whoami • Geoffrey Vaughan @MrVaughan • Security Engineer @SecurityInnovation • Appsec pentesting/advisory at all areas of SDLC • Former High School/Prison/University Teacher • Occasionally I’m let out of my basement • Travelled from Toronto to be here with you today
- 4. IMSI Catchers / Stingrays IMSI Catcher: Can be any rogue cellular device designed to capture cell phone data or traffic Often used by police/governments Stingray - Most popular brand of IMSI Catcher sold to police/governments made by Harris Corp IMSI: International mobile subscriber identity Your unique cell phone ID. Privacy constraints: Strict NDA’s often prevent users from disclosing the device capabilities or naming the device publically (even in case of warrants)
- 6. IMSI Catcher Specs • Can intercept 2G, 3G, 4G communication simultaneously as well as CMDA/GSM networks • Devices can launch attacks requesting devices connect over weaker channels (2G) • Operates in either passive or active mode • Passive mode – Simply captures all available traffic in the area • Active mode – Acts as a full duplex proxy forcing all traffic through the device then onward to a normal cellular tower
- 7. How they are used • Confirming presence of a device in a target’s home prior to a search thereof • Identifying an individual responsible for sending harassing text messages • Locating a stolen mobile device as a precursor to searching homes in the vicinity • Locating specific individuals by driving around a city until a known IMSI is found • Mounted on airplanes by the United States Marshall Service to sweep entire cities for a specific mobile device • To monitor all devices within range of a prison to determine whether prisoners are using cell phones • Reportedly at political protests to identify devices of individuals attending • To monitor activity in the offices of an independent Irish police oversight body Source: https://citizenlab.org/wp-content/uploads/2016/09/20160818-Report- Gone_Opaque.pdf
- 8. Where they are used • 1400+ cases confirmed use in Baltimore mapping show disproportionate use in predominately black neighborhoods' • http://www.citylab.com/crime/2016/10/racial-disparities-in-police- stingray-surveillance-mapped/502715/?utm_source=feed • Thousands of times in Florida since 2007 for crimes as small as 911 hang ups • http://arstechnica.com/tech-policy/2016/08/Baltimore-police-accused- of-illegal-mobile-spectrum-use-with-stingrays/
- 9. Manual Leak The Intercept acquired a device manual and published it: https://theintercept.com/2016/09/12/long-secret-stingray-manuals-detail- how-police-can-spy-on-phones/
- 10. Where to buy • Only sold to governments, police, and military • Alibaba: Good luck (mostly 2G only), Import laws, buyer assumes risk • But for ~1400USD you can build your own: http://arstechnica.com/security/2015/10/low-cost-imsi-catcher-for- 4glte-networks-track-phones-precise-locations/ • Or hide one in a printer and make it call to say I love you https://julianoliver.com/output/stealth-cell-tower
- 11. How to find and detect an IMSI Catcher Current Detection Methods are entirely anomaly based 1. War walk your neighborhood and make note of all Cell Tower ID’s you find and their locations 2. Repeat this until you are sure you have all known devices cataloged 3. Constantly monitor your area to see if any new devices are added 4. Go find the new device
- 12. Tools to help you out OpenCellID.org – Database of mostly user reported cellular tower devices, their location, and their identifiers AISMICD – Android IMSI Catcher Detector app. Tool used to collect cell data. It also reports/syncs with OpenCellID (sometimes). • https://github.com/CellularPrivacy/Android-IMSI-Catcher-Detector Rooted Android Device – Required for AISMICD - Means you need a dedicated device for detection Eric Escobar – Detecting Rogue Cell Towers, built a 50$ device to better triangulate devices (Presented this year) • https://media.defcon.org/DEF%20CON%2024/DEF%20CON%2024%20pr esentations/DEFCON-24-Eric-Escobar-Rogue-Cell-Towers-UPDATED.pdf
- 13. Story Time
- 14. How hostile is it for your devices at Def Con? • Def Con = “Most hostile network on earth” ???? • Sure don’t use the hotel Wi Fi but how bad is it for your cell phones? • Personal experiment to see if I could find any IMSI Catchers
- 15. Setup • AIMSICD App • Burner Android Phone (rooted) • Next time: Pre-install opencellid.org data War Driving the Strip in style
- 16. Don’t Freak out! Pre Def Con War Walk Post Def Con Data
- 17. Lots of false positives • Devices on multiple floors? • Multiple redundant devices in same location • Potential issues with GPS accuracy
- 18. Still Unknown Devices Red dots represent devices that I did not see in my preliminary walk and were not already known to opencellid.org
- 19. Caesar’s • 3 Nights in Caesar’s before Def Con • Lots of towers picked up • Suggest a sort of ‘drive by attack’ • Also observed a lot of LTE to GSM downgrade attacks, my device was hopping networks quite frequently
- 20. Caesar’s • At least 4 of these devices were previously not known to opencellid.org • There were a couple others that had only been seen once before
- 21. Defense • Depends on your personal threat model • Don’t use your device • Wi Fi calling with vpn? • Signal / OpenWhisper app for calling/SMS, although you would still be tracked • If all Wireless Carriers published the tower id’s you could at least know if an id did not match. • Device spoofing would still be possible • Pressure Wireless Carriers to implement mutual authentication between devices
- 22. Conclusions • The devices are very hard to detect, this is part of what makes them so dangerous • You rarely know when you are connected to these devices All data collected is available on my Github Page https://github.com/MrVaughan/Defcon2016GSMData
- 23. Shameless Plug • CMD+CTRL CTF Saturday Night • Accessible web app CTF for beginners and pros a like • Lots of challenges to keep you busy • Prizes
Editor's Notes
- -Talk about 911 impact -Detecting presence -Can break some of the weaker crypto algorithms used in cellular networks
- About Citizen lab: Intersection of Information and Communication Technologies (ICTs), human rights, and global security ‘Cyberwar’ All of these are sourced in Citizen Labs paper
- They are used in Other EU Countries as well as Canada, It is tough getting confirmed uses as it often takes years for the information to trickle out of court cases and information requests Montreal Reporters
- I have it on my calendar to build one in January (first chance I’ll get)
- Looking at your phone right now you have no idea if it is connected to a real cell phone tower or an IMSI catcher
- There are a couple other similar presentations in the last year or 2. Can you trust the data in openCellId ? -If I were XXX -
- Multiple antenna’s