Mobile Handsets:
A Panoramic Overview
Dong Xuan
Associate Professor
CSE Dept., The Ohio State University
Outline
•
•
•
•
•
•
Introduction
Handset Architecture
Handset Operating Systems
Networking
Applications
Security Risks and Mitigation Strategies
What Is A Mobile Handset?
• A mobile handset
(handset) is an electronic
device that provides
services to users, e.g.:
–
–
–
–
Managing address book
Scheduling calendar
Cellular telephony
Accessing Internet, email
• Handsets include
smartphones and PDAs
Example handsets:
Apple iPhone, BlackBerry Storm, Palm TreoPro
Handsets: Your Next Computer?
• Handsets’ small form factor, mobility have
yielded meteoric sales [1]
– 3.3 billion mobile phone subscriptions as of Jan.
2008
– 2.7 billion subscriptions correspond to one
person; some people have multiple phones!
• Rapid replacement rate: young adults replace
phones every 6 months in South Korea [1]
• These statistics are just for phones
• Your handset: your next computer? [2]
What’s Inside a Mobile Handset?
Source: [3]
Handset Architecture (1)
• Handsets use several hardware components:
–
–
–
–
–
–
–
–
Microprocessor
ROM
RAM
Digital signal processor
Radio module
Microphone and speaker
Hardware interfaces
LCD display
Handset Architecture (2)
• Handsets store system data in
electronically-erasable programmable
read-only memory (EEPROM)
– Service providers can reprogram phones
without requiring physical access to memory
chips
• OS is stored in ROM (nonvolatile memory)
• Most handsets also include subscriber
identity module (SIM) cards
Handset Microprocessors
• Handsets use embedded processors
– Intel, ARM architectures dominate market.
Examples include:
• BlackBerry 8700, uses Intel PXA901 chip [4]
• iPhone, uses Samsung ARM 1100 chip [5]
– Low power use and code size are crucial [3]
– Microprocessor vendors often package all the
chip’s functionality in a single chip (packageon-package) for maximum flexibility
Example: The iPhone’s CPU
• The iPhone: a real-world
mobile handset [6–7]
– Runs on Samsung
S3C6400 chip, supports
ARMv6 architecture
– Very few details are known
about the “ARM Core”, esp.
given Apple’s secrecy
– Highly modular
architecture
• Similar to Apple’s iPod
Touch, which lacks
telephony capability [8]
Source: [6]
SIM Cards
• They include their own microprocessor
and 16 KB – 4 MB EEPROM
• They come in two sizes
• Their versatility arises from portability of
information
– SIM card identifies subscriber to network
– Stores personal information, address books,
messages, service-related information
Other Memory Cards
• Some handsets include other peripheral
memory cards:
– Compact Flash
– Multimedia Card
– Secure Digital
• Handsets synchronize with a computer
• Nowadays, computers include slots of
various sizes to hold these memory cards
Handset Operating Systems
• Currently, handsets run several OSes:
–
–
–
–
–
Symbian OS
iPhone OS (an embedded version of OS X)
Windows Mobile
BlackBerry OS
Google Android Platform (based on Linux)
• With the exceptions of Symbian and Android,
these OSes are proprietary [9–10]
• Telecom carriers frequently “lock down” handset
firmware, OSes to prevent user modifications
Handset OS Usage
•
According to British analysis firm Canalys, handset OS
usage in 3Q 2008 had the following ranking (most to
least): [11]
1.
2.
3.
4.
5.
6.
•
•
Symbian OS
iPhone OS
BlackBerry OS
Windows Mobile
Linux (Android, etc.)
Others
iPhone OS surged ahead of BlackBerry OS, but with
new BlackBerries and Android phones, this ranking
may easily change in the future [11]
We’ll now examine each OS individually
Symbian OS
Dominant OS in the mobile handset market
Runs exclusively on ARM processors
Owned by British firm Symbian Ltd.
Descendant of Psion EPOC OS (dev. in 1990s)
Sony Ericsson, Nokia, et al. bought shares in the
firm until Nokia bought Symbian in 2008,
formed Symbian Foundation to further future
open handset development [12]
• Nokia plans to open-source the OS by 2009 [9]
•
•
•
•
•
Design of Symbian OS
• Based on Psion EPOC; desktop OS
features include: [13]
– “Bare-bones” microkernel (nanokernel)
– Pre-emptive multitasking
– Memory protection
• Handset-centric design, can operate
several months without reboot
• Supports multiple UIs based on
smartphone form factor (e.g., 320 × 240)
Symbian OS Devices
• Numerous handsets use Symbian OS; UIs largely
based on manufacturer & device
– Nokia S60: includes J2ME, std. UI (mostly Nokia
phones)
– Nokia S80: QWERTY keyboard, Web browser,
enterprise office-doc. support (older Nokia
Communicators)
– Nokia S90: used only on Nokia 7710
– UIQ: Sony Ericsson/Motorola GUI platform used
primarily on those companies’ handsets
– FOMA platform: closed-dev. software platform used
by handsets on NTT DoCoMo’s network (Japan)
Symbian OS v9 Architecture
Source: [15] (heavily modified)
Symbian OS Development
• Native language is C++
– Nokia provides free Eclipse-based Carbide.c++
development tools, Carbide.vs Visual Studio plugin
– Mac & Linux development is possible
• Can program in many other languages: C, Java,
Ruby, Python, Perl, OPL, Visual Basic, Simkin
• Applications needing any capabilities beyond
bare minimum must be cryptographically signed
(see http://www.symbiansigned.com)
• Can also program in Adobe Flash Lite (mobile
version of Flash)
iPhone OS
• Runs on both the iPhone and iPod Touch
• Variation of Mach microkernel-based OS X that
fits in 512 MB flash memory, runs on ARM
architecture [21]
• Four abstraction layers: Core OS, Core Services,
Media, Cocoa Touch [22]
• Core Animation and PowerVR MBX 3D
hardware provide interface animations
• 320 × 480 LCD display that supports multitouch gestures
iPhone Developer Program
• iPhone Developer Program provides dev. tools,
iPhone emulator, means to upload to App Store
(SDK)
• To download SDK, you must apply to be a
member, pay fees
– Standard Developer: $99
– Enterprise Developer: $299
– Exception: Apple’s free iPhone Developer University
Program for higher-ed. institutions [23]
• SDK only runs on Mac OS X Leopard on Intelbased Macs (go figure)
iPhone Web App Development
• You can develop Web apps for iPhone – so long as they
run on Safari [24]
• Safari features: [25–26]
– Auto-resizes Web pages to fit browser size
– Multi-touch functionality
– XHTML 1.1, CSS 2.1, JavaScript, W3C DOM Level 2, AJAX
technology, cookies, …
• Does not support Flash or Java
• iPhone Web apps should:
– Minimize user awareness of browser experience
– Reproduce control style, layout, behavior of iPhone apps
– Integrate with built-in iPhone features & services
BlackBerry OS
• BlackBerry OS is Research in Motion’s (RIM’s)
proprietary OS for its BlackBerry handsets
• Provides multitasking, heavily uses BlackBerry
input devices, e.g., thumbwheel
• Current OS 4 provides a subset of Java’s Mobile
Information Device Profile (MIDP) 2.0
• Developers can use these APIs, proprietary APIs
to write software
• All applications must be digitally signed so to
“link” an app with the developer
BlackBerry Software
• Email from BlackBerry service, MS Exchange, Domino,
Yahoo, etc. can be “pushed” to the handset
• Can view PDF, MS Word, Excel, PowerPoint attachments
• BlackBerry Browser (only supports JavaScript)
• Other online apps include:
– BlackBerry Maps
– Facebook services
– Yahoo Messenger, Google Talk
• Calendar, Address Book, and PIM Sync via USB
• GPS
• See http://www.blackberry.com for much more
information about handset and desktop software
BlackBerry Wireless Platform
• RIM provides standards-based platform
and developer tools to develop and deploy
custom wireless applications
– HTML Web browser
– Java Mobile Edition development tools
– .NET applications
• BlackBerry handsets support standard
networking protocols and connect to any
type of server application
BlackBerry Mobile Data System
• BlackBerry Mobile Data System (MDS) supports MS
Exchange, Lotus Domino, Novell GroupWire, and RIM’s
own MDS systems for messaging applications
BlackBerry Mobile Voice System
• With this service, there’s only one business
number BlackBerry users must remember
• Calls are routed to a BlackBerry handset,
regardless of whether the call is directed to an
office or mobile phone [27]
• Provides security and authentication through
BlackBerry Enterprise Servers [28]
• IT administrators can lock down handsets, route
calls through their telecom infrastructure, etc.
[27–28]
BlackBerry Internet Services
• BlackBerry Internet Service leverages centrally-hosted
wireless gateways, allowing users to access up to 10
supported email accounts, browse Internet
BlackBerry Developer Tools
• RIM provides several development tools:
– BlackBerry MDS Studio
• Developers can quickly create rich client apps using
component-based drag-and-drop approach
• Tool requires MDS runtime
– BlackBerry plugin for MS Visual Studio (development
on MDS platform)
– BlackBerry Java Development Environment (JDE)
• Provides IDE, simulation tools for Java ME app for Javabased BlackBerry so developers can create standalone or
client-server apps
Windows Mobile
• Windows Mobile is powered by Microsoft’s
Windows CE embedded OS; Windows CE runs
on x86, MIPS, ARM, Hitachi SuperH processors
• Latest version, 6.1, includes Windows Live
services, Exchange 2007 mail access
• Designed to closely mimic desktop Windows:
– Windows Mobile 6.1 includes mobile versions of
Office applications, Outlook (w/HTML email),
Internet Explorer, Windows Media Player
– SQL Server 2005 included in ROM
– .NET Compact Framework 2.0 included
Windows Mobile Development (1)
•
•
Native code is developed with MS
Visual C++
Microsoft strongly recommends
development with managed code
[19]
–
–
–
•
Managed code is written in one of the
.NET framework object-oriented
languages
Compiled to MS Intermediate
Language (MSIL) that all the languages
share
At execution time, MSIL is compiled
“just in time” to native object code
Contrast with Java:
–
–
Java code is compiled to Java bytecode
Java interpreter interprets bytecode,
dynamically compiles frequentlyaccessed bytecode into native object
code (HotSpot)
.NET Framework in Context. Source: [19]
Windows Mobile Development (2)
• Windows Mobile development tools
include:
– Plugins for MS Visual Studio 2005, 2008, etc.
– SDKs for Windows Mobile-based handsets
– Microsoft gives away Visual Studio to students
for free with its DreamSpark program [20]
Android Mobile Handset Platform
•
•
Android is a software
development platform for mobile
handsets that is based on Linux
Developed by Google and Open
Handset Alliance (OHA) for
different handset manufacturers
– The Alliance includes T-Mobile,
Sprint Nextel, Google, Intel,
Samsung, Wind River Systems, et
al. [29]
– Its purpose is to build a fully free
and open mobile handset platform
to facilitate development of
handsets, software, services [30]
•
First Android-based handset is TMobile G1 [31]
Android Architecture
Android Features and Software
• Features
3D: OpenGL ES 1.0
SQLite: Database engine
WebKit: Web browser
Dalvik: Register-based VM
similar to Java VM [32]
– FreeType: Bitmap and vector
font rendering
– Connectivity: Bluetooth,
802.11, GPS
–
–
–
–
• Core Applications
– Email client, SMS program,
calendar, Google Maps (and
Apps), browser, etc.
– Written in Java
• App Framework
– Full access to same framework
APIs
– Architecture designed for
component reuse
• Runtime
– Core C++ library
– Multiple Dalvik VMs run in a
process, rely on Linux kernel
for process isolation [32]
Android SDK
• Android SDK provides required tools and APIs
to develop apps on Android platform using Java
– Android is licensed under the Apache open-source
license
– The Android Development Tools (ADT) Eclipse plugin
eases development
– Download the Android SDK at
http://code.google.com/android/ and the Eclipse
plugin at https://dl-ssl.google.com/android/eclipse
Palm OS
• Palm OS originally designed by Palm Computing
Inc. for Palm handsets, sold to Japanese firm
ACCESS [16]
• From Jan. 2004 – Jun. 2005, there has been no
development on Palm OS past v6.1 [16]
• ACCESS and Palm are working on new versions
of the OS that are Linux-based [16]
– ACCESS’ version is called the ACCESS Linux Platform
– Palm’s version will be called Palm OS; should be
available Q1 2009
Handset Networking
• Handsets communicate with each other
and with service providers via many
networking technologies
• There are two “classes” of these
technologies:
– Cellular telephony
– Wireless networking
• Most handsets support both, some also
support physical connections such as USB
Cellular Telephony Basics (1)
• There are many types of cellular services; before delving into
details, focus on basics (helps navigate the “acronym soup”)
• Cellular telephony is a radio-based technology; radio waves
are electromagnetic waves that antennas propagate
• Most signals are in the 850 MHz, 900 MHz, 1800 MHz, and
1900 MHz frequency bands
Cell phones operate in this frequency range
(note the logarithmic scale)
Cellular Telephony Basics (2)
• Digital signal
processors (DSPs) are
key to radio reception
in handsets
• They transform
signals from one form
to another, e.g.:
– Fourier transforms
– Discrete cosine
transform
Source: [3]
Cellular Telephony Basics (3)
• Cells and base stations
– Space is divided into cells,
and each cell has a base
station (tower and radio
equipment)
– Base stations coordinate
themselves so mobile users
can access the network
– If you move from one cell
to another, the first cell
notices your signal strength
decreasing, the second cell
notices your signal strength
increasing, and they
coordinate handover so
your handset switches to
the latter cell
Cellular Telephony Basics (4)
• Statistical multiplexing
– Time Division Multiple Access (TDMA)
• A 30 kHz-wide and 6.7 ms-long band is split into 3 time slots
• Each conversation gets the radio 1/3 of the time; voice data is
converted to digital information and compressed to use less
transmission space
Cellular Telephony Basics (5)
• Statistical multiplexing cont’d.
– Frequency Division Multiple Access (FDMA)
• Analogous to TDMA, but each conversation uses a
different frequency in the same band
– Code Division Multiple Access (CDMA) [38]
• Uses spread-spectrum technology and different
pseudo-noise codes so multiple users share the
same physical channel
Cellular Telephony
• It is useful to think of cellular telephony in terms
of generations: [33–37]
0G: Briefcase-size mobile radio telephones
1G: Analog cellular telephony
2G: Digital cellular telephony
3G: High-speed digital cellular telephony (including
video telephony)
– 4G: IP-based “anytime, anywhere” voice, data, and
multimedia telephony at faster data rates than 3G
(to be deployed in 2012–2015)
–
–
–
–
• We will focus on 2G and 3G technologies
Cellular Telephony – 2G
• There are two main 2G technologies:
– Global System for Mobile communications
(GSM), which uses TDMA [39]
– Interim Standard 95 (IS-95, aka cdmaOne™),
which uses CDMA [40]
• There are other TDMA networks such as
PDC (Japan-only), iDEN (Nextel-only),
and IS-136 (now converted to GSM)
• We won’t worry about these
GSM (1)
GSM network architecture includes the following subsystems:
•
Mobile Stations (MSes) –
handsets
•
– Each handset has a SIM card
•
– Composed of several Mobile
Switching Centers (MSC) in
conjunction with location registers
(Home Location Registers –
HLRs, Visitor Location Register –
VLRs) and authentication centers
(AUCs)
Base Station Subsystems (BSSes)
– provide air link for MSes
– A BSS consists of a Base Station
Controller (BSC), which includes
the TransCoder Unit (TCU) and
the Base Transceiver System
(BTS)
– A BSC controls several BTSes,
which is responsible for
communication with the NSS and
OSS
Network SubSystems (NSSes) –
connect calls between network
users
•
Operation SubSystems (OSSes) –
provide network admins with
remote network monitoring,
mgmt. capabilities
– Operations & Maintenance Center
(OMC) provides network with
remote monitoring, maintenance
as well as alarms, event logging
GSM (2)
• GSM network architecture is as follows:
GSM (3)
• Short Message Service (SMS) [41]
– 1985 GSM standard that allows messages of at most 160 chars.
(incl. spaces) to be sent between handsets and other stations
– Over 2.4 billion people use it; multi-billion $ industry
• General Packet Radio Service (GPRS)
– GSM upgrade that provides IP-based packet data transmission
up to 114 kbps
– Users can “simultaneously” make calls and send data
– GPRS provides “always on” Internet access and the Multimedia
Messaging Service (MMS) whereby users can send rich text,
audio, video messages to each other [42]
– Performance degrades as number of users increase
– GPRS is an example of 2.5G telephony – 2G service similar to 3G
GSM (4)
• Enhanced Data rate for GSM Evolution
(EDGE) [43]
– GSM revision that provides 3× GPRS’ data
rate (max. 236.8 kbps); considered 3G tech.
– Deployed on GSM networks starting in 2003
– EDGE Evolution increases bit rates to
(theoretical) max. of 1 Mbps, decreases
latency from 200 ms to 100 ms
IS-95, CDMA2000, and 3G
• Qualcomm developed IS-95 in the 1990s as first CDMAbased mobile standard [40]
• Unlike GSM, which is open, Qualcomm owns patents on
CDMA technology
• CDMA2000, IS-95’s hybrid 2.5G/3G successor, is
supplanting it [44]
• The Telecommunications Industry Association owns the
trademarks “cdmaOne” and “CDMA2000” in the U.S.
• There are two competing 3G technologies: the Universal
Mobile Telecommunications System (UMTS) and
CDMA2000
UMTS and HSPA
• The UMTS is an international standard designed to
replace GSM (aka 3GSM) [45]
• UMTS is a 3G standard and is being developed into a 4G
standard
• Its air interface is Wideband CDMA (W-CDMA), which
was developed by NTT DoCoMo for Japan’s 3G wireless
network [46]
• W-CDMA has been deployed in Europe and Asia
• In theory, High Speed Packet Access (HSPA) protocols
extend UTMS’ performance to 14.4 Mbps and 5.76 Mbps
downlink and uplink, respectively [47]
• In practice, max speeds are 7.2 Mbps and 1.4 – 5.8 Mbps,
respectively (depending on carrier)
Other Handset Networks
• Many handsets not only support cellular
telephony, they support other networking
technologies as well:
– Wireless
• Bluetooth (100 m max, 10 m for handsets)
• IEEE 802.11 (longer range)
• Infrared Data Association (IrDA)
– Wired
• USB, etc.
Bluetooth (1)
• Bluetooth is a technology specification for small
form factor, low-cost, short-range wireless links
between mobile handsets, Internet connectivity
• Max range is 100 m in 2.4 GHz frequency band
(handsets: 10 m radios)
• There is possible interference with IEEE 802.11b
WLANs operating in this band
• Max bandwidth is 3 Mbps for Bluetooth 2.x with
Enhanced Data Rate
Bluetooth (2)
• Link Types
– Synchronous Connection-Oriented (SCO)
• Useful for circuit-switched services, e.g., voice, where low delay and
high QoS are required
• Offered channels are symmetric and synchronous
– Asynchronous Connection-Less (ACL)
• More efficient for data transfer, other async. services
• Link offers packet switching, transmission (Xmission) slots granted
by polling access scheme
• A piconet is a collection of up to 8 Bluetooth units where one is a
master that controls Xmission, hopping scheme, others are slaves
– Master tells slave, “I want to send,” and slave receives
– Slaves can send on slots only when they agree with master
– One connection can have several links of either type, but there’s
a 3 voice call limit within a piconet
Bluetooth (3)
• Piconets and scatternets
– One device can be connected in two or more
piconets, which is termed a scatternet
• But a device can only be a master to one piconet at
a time
• In order for device to be part of scatternet, support
for hold, park, or sniff mode is needed
– Master/slave roles are not necessarily fixed
and can be changed during connection
– Master/slave switch needed in scatternet
Bluetooth (4)
• Piconets and scatternets, cont’d.
– a) Point-to-point connection between two devices
– b) Point-to-multipoint connection between a master and three slaves
– c) Scatternet consisting of three piconets
Bluetooth (5)
• Bluetooth uses adaptive frequency hopping (AFQ) that
detects other devices in the frequency spectrum and
“hops” among 79 channels 1 MHz apart to reduce
interference [48]
Bluetooth (6)
•
•
•
•
Connections established via page messages; if recipient address is
unknown, master’s inquiry message is needed (that gives access code, asks
for slave’s Bluetooth address and system clock)
Units are in standby mode before connections are made
Page message is sent on 16 frequencies 128 times; if no response, message is
sent on 16 different frequencies 128 times
Max. connection time is 2.56 seconds
Bluetooth (7)
• Bluetooth Special Interest Group (SIG)
has defined numerous usage models for
the technology that describe primary
Bluetooth applications & intended devices
• Profiles define the protocols & protocol
features that support a usage model
• See [49] for more information
IEEE 802.11 Networks
• The IEEE 802.11 standards specify how
electronic devices communicate with each other
in wireless fidelity (Wi-Fi) networks
• Many handsets can communicate with each
other this way
• There are many 802.11 standards [53]; we’ll only
look at 802.11b, 802.11g, and WiMax here
• Other 802.11 standards provide greater security,
which we’ll discuss later
IEEE 802.11 & WiMax Specs.
• 802.11b (1999): [51, 53]
– Operates in the 2.4 GHz frequency band
– Provides max 11 Mbps data rate
– 38 m indoor range
• 802.11g (2003): [51, 53]
– Operates in either 2.4 GHz or 5 GHz frequency bands
– Provides max 54 Mbps data rate
– 38 m indoor range
• WiMax (802.16): [52]
– Operates in 2.3 GHz, 2.5 – 2.6 GHz frequency bands
– Provides max 40 Mbps data rate now, 300 Mbps later
– 3 km cell range
IrDA
• The Infrared Data Association (IrDA) provides
protocols to transfer data between handsets,
other devices using infrared light [54]
– Similar in principle to a remote control
– Data rate is 16 Mbps now, 300 – 500 Mbps later
– Range is 1 m, communicating devices must have a
“line of sight”
– Deployed in over 500 million devices
Wired Networks: USB
• The Universal Serial Bus (USB) is a ubiquitous
standard for transferring data between
computers (including handsets!) [55]
– By definition, data is transferred one bit at a time
– USB 1.1 (1998): max 1.5 Mbps (low-speed), 12 Mbps
(full-speed)
– USB 2.0 (2000): max 480 Mbps
– USB 3.0 (to be released in 2009 – 2010): max 5 Gbps
Handset Applications
• Many handset applications mirror those of
computers, e.g., managing one’s schedule, Web
browsing, etc.
• But handsets’ mobility is opening up new
markets
– Global mobile gaming market value expected to reach
€2.6 billion ($3.27 billion) in 2012
– Global mobile advertising market value expected to
reach €1.77 billion ($2.23 billion) in 2012
• Also, handsets make mobile and location-based
services possible, which we’ll discuss next
Mobile & Location-based Services
• Carnegie Mellon University’s (CMU’s) Human Computer Interaction
Institute has developed several such services that we’ll examine
– Mobile social computing
• inTouch: Coordination for families, small groups
• Whisper Mobile: Coordinating groups for social events
– Large-scale mobile collaboration
• Hitchhiking: estimating places’ busyness
– Mobile data
• GurunGo: Linking desktop, mobile devices
– Usable privacy and security
• Contextual instant messaging
• People Finder
• CMU’s Grey resource-control system
– Memory support
• Memory karaoke
Mobile Social Computing
• Mobile social computing
– inTouch: Coordination for families, small groups
– Whisper Mobile: Coordinating groups for social events
• Large-scale mobile collaboration
– Hitchhiking: estimating places’ busyness
• Mobile data
– GurunGo: Linking desktop, mobile devices
• Usable privacy and security
– Contextual instant messaging
– CMU’s Grey resource-control system
inTouch (1)
The inTouch service helps coordinate with others while mobile
Target Users:
Mobility
•
•
•
Small to medium groups of people
Fluid & demanding schedule
Many responsibilities
Examples:
Messaging
Awareness
•
•
•
Dual-career families
Work groups
Ad hoc (e.g., conferences)
inTouch (2)
inTouch use case: Suppose Vanessa is running late picking
up her son Daniel. She can send him a text message
telling him that she’ll be 15 minutes late.
Daniel
Whisper Mobile (1)
Motivation: Easily find, share, and coordinate friends for social events
Whisper Mobile (2)
•
Creating an event is straightforward
– Minimal text input
– Use location, audio, camera to do so
•
Then link it with inTouch
(a)
(b)
(d)
(c)
(e)
Large-Scale Mobile Collaboration
• Mobile social computing
– inTouch: Coordination for families, small groups
– Whisper Mobile: Coordinating groups for social events
• Large-scale mobile collaboration
– Hitchhiking: estimating places’ busyness
• Mobile data
– GurunGo: Linking desktop, mobile devices
• Usable privacy and security
– Contextual instant messaging
– CMU’s Grey resource-control system
Hitchhiking (1)
• Many location-based services focus on
“where you are”
• Hitchhiking looks at places’ busyness, e.g.,
– “Is the café busy?”
– “How long are the airport lines?”
• Approach: estimate number of people in a place
by counting number of handsets there and
upload number and location to servers
(anonymized for privacy)
• Locations can be viewed on a map, e.g.,
Microsoft’s SensorMap
Hitchhiking (2)
Mobile Data
• Mobile social computing
– inTouch: Coordination for families, small groups
– Whisper Mobile: Coordinating groups for social events
• Large-scale mobile collaboration
– Hitchhiking: estimating places’ busyness
• Mobile data
– GurunGo: Linking desktop, mobile devices
• Usable privacy and security
– Contextual instant messaging
– CMU’s Grey resource-control system
GurunGo (1)
• Goal: Easily access useful info while mobile
• Motivations:
– People print out online maps rather than copy them
to handset (easier, small mobile form factor)
– People browse the Web differently on desktops and
handsets
• GurunGo allows people to explicitly copy info to
handsets, implicitly copy maps to handsets and
generate speech-based directions
GurunGo (2)
Example of speech-based directions:
Usable Privacy and Security
• Mobile social computing
– inTouch: Coordination for families, small groups
– Whisper Mobile: Coordinating groups for social events
• Large-scale mobile collaboration
– Hitchhiking: estimating places’ busyness
• Mobile data
– GurunGo: Linking desktop, mobile devices
• Usable privacy and security
– Contextual instant messaging
– CMU’s Grey resource-control system
Contextual Instant Messaging
• CMU developed a custom
AIM client, bot that
people can query
“howbusyis screenname”
• Robot respects userspecified privacy settings
– Users can create groups,
put screen names in them
– Users can specify what
each group can see
• System generates audit
logs for security
Grey Resource Control
•
CMU developed a distributed
handset-based resource control
system
– Resources include office doors,
electronic files, etc.
•
Flexible, end user-specified
policies:
– Proactive: Manually create policy
before request, e.g., “Alice can
always enter my office”
– Reactive: Generates policy based
on request, e.g., “Can I enter your
office?”
•
•
CMU connected Grey with
Bluetooth-enabled office doors
There were security and usability
issues with the system
A Large-Scale Mobile App
Gawker Stalker – people spotting celebrities in New York City
Handset Security Issues (1)
• People store a wealth of information on their handsets
and don’t think about securing them!
• Naturally, this makes handsets targets for miscreants –
whether they’re “script kiddies” or Mafia cybercriminals
– due to what’s stored on them:
–
–
–
–
–
–
–
Incoming, outgoing, missed calls
SMS (text) and MMS messages
E-mail
Instant-messaging (IM) logs
Multimedia, e.g., pictures, music, videos
Personal calendars
Address books
• Clearly, handset security is a vitally important challenge
Handset Malware History (1)
• Hackers are already attacking handsets
– Most well-known case: a 17-year-old broke
into Paris Hilton’s Sidekick handset [58]
– Less well-known: worms, viruses, and Trojans
have targeted handsets since 2004
• 2004: [59]
– Cabir worm released by “29A,” targets Symbian phones
via Bluetooth
– Duts virus, released by same group, targets Windows
Mobile phones
– Brador Trojan released by same group, opens backdoor
on Windows Mobile [63]
Handset Malware History (2)
• 2005: [60]
– CommWarrior worm released; replicates via Bluetooth, MMS messages
to all contacts in address book
– Doomboot Trojan released; claims to be “Doom 2” video game, installs
Cabir and CommWarrior
• 2006: [59–60]
– RedBrowser Trojan released; claims to be a Java program, secretly
sends premium-rate SMS messages to a Russian phone number
– FlexiSpy spyware released; sends log of phone calls, copies of
SMS/MMS messages to Internet server for third party to view
• 2008: [61]
– First iPhone Trojan released
– Of course, other mobile malware has been released; some
malware completely disables the handset
– There is also the possibility of mobile botnets [62]
Key Handset Security Problems
• “At this point, mobile device capability is far ahead of security.”
– Prof. Patrick Traynor, Georgia Tech (emphasis added) [62]
• Handset information can be stolen [63]
– Transient information: Enhanced 911 can provide user location
information
– Static information: “BlueSnarfing” attacks (connection without
owner’s knowledge), cracking Wired Equivalent Privacy (WEP) and
Wi-Fi Protected Access (WPA) [64]
• Theft of service attacks, e.g., premium-rate calls/SMS messages [63]
• Denial-of-service attacks [63]
– Flooding attacks overload the handset radio with garbage
– Power-draining attacks attempt to drain the battery
• Botnets and DoS attacks against networks are likely in the future [62]
• Cybercriminals make 10× as much as security researchers! [69]
Mitigation Strategies
• Handset manufacturers, OS & software vendors, and researchers
have worked to counter threats
– Symbian OS requires apps to be cryptographically signed in order for
them to run without user approval
– Some handset manufacturers have joined the Trusted Computing Group
(TCG) and added hardware to thwart malware tampering with the
device [60]
– The iPhone runs each application in a “sandbox” to prevent malware
from running on the device [68]
– Heterogeneous handset OSes make massive malware outbreaks difficult
– Vendors like McAfee, Symantec, and Trend Micro sell security software
for handsets; F-Secure has bundled its software with Hong Kong
provider CSL’s handsets [65]
– Researchers have worked on modeling malware propagation on
networks, detecting power-draining attacks, etc. [66–67]
The Challenges Ahead
• “[Because] the mobile communications field is evolving so quickly, it
presents a unique opportunity to design security properly—an
opportunity we missed with the PC.” – Prof. Patrick Traynor [62]
• Since most people buy a new handset every 2 years, it’s vital to
ensure the security of handset hardware, OSes, applications, and
networks while maintaining usability [62]
• One suggested approach is to give handsets a “hard” power-off
switch so they don’t have power when turned off [63]]
• Academic research will play a key role in this, as will user education
to counter social engineering
• Given the sensitivity of information stored on handsets,
cybercriminals may well find effective ways to use them to continue
their nefarious acts, e.g., bot herding, data theft, etc., even with
different operating systems, power constraints, and carriers
• Though we may not hear news of handset attacks as often as those
against (Windows) PCs, we cannot fall into a false sense of security
Questions?
Thank you!
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