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- [Lecturer] Google actually
includes security features

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and work with developers
and device implementers,

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to keep the Android
platform and the ecosystem

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in a safe environment.

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So and again, it's not so much

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only about the actual Android platform,

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so your mobile device or your
tablet or your refrigerator,

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whatever the case is
actually running Android,

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but also as far as actually ecosystem.

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How you're connecting to the app stores,

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how you interact with APIs
and so on and so forth.

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Now, the beauty is that Android

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of course is designed to be open.

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One of the challenges is of course

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is little bit less control
than other alternatives,

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like of course, Apple iOS.

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Now, Google tries to
maintain the Android platform

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to offer an application environment

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to help protect the confidentiality

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and of course, integrity
and availability of users,

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and also of the data and the applications

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and the actual device itself,

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and as I mentioned before the ecosystem,

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so the network.

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Now, both Apple and Google have
dedicated a lot of resources

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to make their mobile operating systems

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sort of, fairly secure.

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Some of the main challenges in security

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is whenever the users
root their devices rather

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or jailbreak their devices
and leaving them open

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to either malware or
compromise applications.

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Now, the main Android
platform building blocks

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are of course, the device hardware,

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that runs on terms of hardware,

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so that includes your
smartphone, your tablet

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of course watches, so smart watches, cars,

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smart TVs, gaming systems, refrigerators,

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you name it.

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A lot of things actually
run Android nowadays.

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Now, the other beauty is that
Android is processor-agnostic,

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but it does take advantage

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of some of the hardware-specific
security capabilities,

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especially in the ARM architecture.

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So, and there's actually
a security capability

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called ARM eXecute-Never,

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it prevents a remote execution
or arbitrary execution

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of any type of buffer or flows perhaps

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that actually can be
exploited in the system.

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Now, the Android operating
system of course,

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is the core operating system

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and it's actually built on
top of the Linux Kernel,

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so it's all based on Linux.

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All device resources like
the camera, GPS, Bluetooth,

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wifi, the telephony functions,
the network connectivity,

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and you know, many more,

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are accessed via the
operating system itself,

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via the core Android functionalities.

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Now, you also have of course,

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the Android application runtime,

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so, Android applications
are actually most often

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written in the Java programming language

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and they actually run
in the Android runtime

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and they refer to this as the ART.

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However, many applications,

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including the core Android
services and other applications,

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are actually native applications
or include native libraries

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within the operating system itself.

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Now, the Android applications extend

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the core Android opening system,

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and there are two primary
sources for these applications,

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so the pre-installed applications
that come with your device

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or the user-installed applications

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via the Google Play or any other stores,

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of course, that can be accessed

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mostly if you root the device,

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and that's the problem with
security as I mentioned before.

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Now, Google provides a set
of cloud based services

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that are available to different
compatible Android devices

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and these services are not part

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of the Android Open Source Project itself,

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but they're included into many
different Android devices,

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so, but of course, you know,

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we have the primary service
for installing applications

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or the actual store, which is Google Play,

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you also have the services
to actually push updates,

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which is called Android Updates,

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again, it's a update service
that provides new features

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and security updates
through either the web

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or through over-the-air
or OTA functionality.

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So now, there's also
the Application Services

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and basically it's a framework that allows

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Android applications to
use cloud capabilities,

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like, backing-up your application data,

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backing-up your settings.

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And also, they have a
Cloud-to-Device messaging,

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that is called C2DM that is actually used

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for pushing messaging
to the cloud as well.

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They also have another
service called Verify Apps

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and it basically, it can warn you,

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or automatically block the installation

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of any type of a compromise applications

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or any harmful applications.

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And also, it continuously scan
applications on the device,

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warning about or removing those
applications automatically.

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Another service is the SafetyNet,

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so and again, I'm mentioning all this

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because whenever you do security research

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or whenever you're actually trying to do

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"mobile device ping testing"

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which by the way, is way
different than let's say,

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if you're trying to actually
do ping testing on wifi,

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in this case, you actually have to look

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at many different things.

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You have to look at these services

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that I'm mentioning right now,

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you have to look at the ecosystem

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and we're gonna cover that
throughout the course.

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So, now going back to the services,

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the other one is SafetyNet,

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and it's basically a privacy preserving,

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well, some people call it
Intrusion Detection System

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to assist Google tracking and mitigating,

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known security threats

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and also to identify other
types of abnormalities,

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by far is not an
Abnormally Detection System

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as you probably are familiar with,

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that's why a lot of people

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actually call it an
Intrusion Detection System

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within the Android ecosystem.

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And now, part of that is
actually the SafetyNet

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at the station service,

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basically allows for third-party APIs

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to determine whether the
device is CTS compatible

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and also can assist
identify the Android app

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communicating with the app server.

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So, whenever somebody actually
creates an app that perhaps

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is communicating to the
cloud, to the app server,

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let's say, I don't know,

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Uber, Lyft, OpenTable,

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whatever you actually use
in your Android device,

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that's the type of SafetyNet attestation

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that in some cases actually is available

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and implementers actually
take advantage of,

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to determine whether the device
is actually CTS compatible

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and also allow for the
security of third-party APIs.

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Now, there's also the Device Manager,

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so the Android's Device Manager

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and is a web app and also an Android app

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that is actually used to
locate lost or stolen devices,

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fairly similar to what Apple
has with Find My Device.

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Now, the Android security
model is actually based in part

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on the concept of application sandboxes,

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and each application runs its own sandbox.

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Now, a long time ago, several years ago,

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prior to Android version 4.3,

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these sandboxes were defined

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by the creation of a unique Linux UID,

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and that UID was actually
for each application

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at the time of the installation.

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Now from 4.3, so for quite some time,

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now Android actually uses SELinux,

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so the Security-Enhanced Linux.

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This is actually used for
defining the boundaries

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of the application sandbox in Android.

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Now, as part of the
Android security model,

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Android uses SELinux

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to enforce Mandatory Access Control, MAC,

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over all processes,

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even processes running with a root

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or super privileges or
superuser privileges,

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this actually helps protect
the operating system.

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Also SELinux enhance Android

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by confining privileged processes

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and automating the Security
Policy creation on that device.

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Now, Android also includes
SELinux in Enforcing mode

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and basically, a
corresponding Security Policy

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that works by default
across those devices.

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So now, in Enforcing mode,

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and this is actually something
you have to keep in mind

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whenever you're actually
doing security research

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in Android platforms.

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You know, in Enforcing mode,

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illegitimate actions
are prevented by default

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and all attempted violations
are actually logged

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by the kernel to dmesg and also logcat.

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Android devices manufacturers

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should actually gather
information about these errors,

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so they can actually refine their software

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and their own SELinux processes
before enforcing them,

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however, unfortunately this
doesn't happen all the time.

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That's one of the major differences

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between Apple iOS devices and Android.

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And again, I'm not by far an
Apple fanboy in this case,

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but unfortunately,

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that's actually one of
the major difference,

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is that because Android of course,

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Google provides the operating system

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but it's up to the implementers

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to actually do a few of these
security implementations,

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some implementations may
be more secure than others.

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Now by default, on Android only the kernel

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and a small subset of
the core applications

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run with root per permissions.

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Now, Android does not prevent the user

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or an application with root permissions

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from modifying the operating system,

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can also modify the kernel
or any other application.

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So in general, root has full
access to all applications

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and all application data.

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So that's whenever users
that actually change

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their permissions on an Android device

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to grant root access to applications,

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definitely increase the security exposure

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to malicious applications and
potential application flaws,

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and that's whenever you see a lot

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of impersonated applications and so on.

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So again, a lot of people that
actually root their devices,

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I hate to say this but they're
actually asking for it.

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Now, some implementers
may actually change that.

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Another thing to actually
keep in mind is that,

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whenever you're doing security
research on Android devices,

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so in a lot of cases,
actually a lot of people,

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actually what they do is,

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they start from just by
rooting their device.

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Now, the ability to modify an
Android device that you own

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it's important developers working
with the Android platform,

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so on many Android devices,

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user users actually have the
capability or the ability

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to unlock the bootloader in
order to allow the installation

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of some other alternate operating system,

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so some we call it custom ROMS.

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And this alternate operating systems

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may actually allow a user
to actually gain root access

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for the purpose of debugging, "debugging"

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and then system components
to actually access features

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that are not present to applications

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by the Android APIs by default.

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Now, let's switch a little bit,

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let's actually talk about encryption,

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and specifically, encryption at rest.

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Now, Android version 5.0 and later,

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so for quite some time,

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they actually support
full-disk encryption.

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And then from Android 7.0 and later,

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it actually supports
file-based encryption as well,

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and basically, file-based
encryption allows different files

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of course, to be encrypted
with different keys

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that can be used to be decrypted

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or unlocked independently.

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And another thing is actually about,

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another thing that I
want to cover here is,

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application signing.

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So, what about application signing?

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Application signing allows developers

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to identify the author of the application,

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so to making

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that the user knows

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that the application
is actually legitimate

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and to update their application

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without creating complicated
interfaces or permissions.

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Now, every application that is
run on the Android platform,

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by default must be
signed by the developer.

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Of course, if you root it and
you go to some other store,

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that's definitely very different, right?

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Now, applications that actually attempt

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to install without being signed,

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by default, again will be
rejected by either Google Play

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or the package installer
on the Android device.

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If you go to another store

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and if you actually root the device,

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then that's completely different again.

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Now on Google Play,

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developers know their application

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it's actually provided by them or modified

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00:14:00,490 --> 00:14:03,510
and that the Android
device and the developers

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00:14:03,510 --> 00:14:05,410
actually can be held accountable

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for the behavior of their application.

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But of course, if it's
modified, then all bats are off.

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00:14:12,040 --> 00:14:15,020
Now, on Android application
signing is the first step

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to placing an application
in its application sandbox.

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The signed application
certificates define which user ID

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00:14:23,540 --> 00:14:27,230
is actually associated
with which applications

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00:14:27,230 --> 00:14:28,960
and then, different applications

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00:14:28,960 --> 00:14:31,690
run under different user IDs.

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00:14:31,690 --> 00:14:33,520
Now, application signing ensures

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00:14:33,520 --> 00:14:37,120
that one application cannot
access another application

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00:14:37,120 --> 00:14:40,213
accept through a well defined IPC.

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00:14:41,150 --> 00:14:43,983
Now, when an application or APK files,

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00:14:43,983 --> 00:14:47,150
basically, applications are APK files,

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00:14:47,150 --> 00:14:50,200
whenever these are installed
on an Android device,

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00:14:50,200 --> 00:14:54,710
the PackageManager is the
entity that actually verifies

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00:14:54,710 --> 00:14:57,102
that the APK has been properly signed

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00:14:57,102 --> 00:15:01,170
and with the certificate
included in the APK.

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00:15:01,170 --> 00:15:03,960
If the certificate or more accurately,

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00:15:03,960 --> 00:15:08,030
the actual public key
certificate matches the key

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00:15:08,030 --> 00:15:11,640
that is actually used to sign
any other APK on the device,

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00:15:11,640 --> 00:15:16,480
the new APK actually has the
option to specify the manifest

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00:15:16,480 --> 00:15:18,750
that it will actually share a user ID

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00:15:18,750 --> 00:15:23,670
with other similarly signed APKs.

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00:15:23,670 --> 00:15:28,307
Now, applications can be
signed by third-party OEMs

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00:15:30,290 --> 00:15:33,510
or any other type of marketplaces.

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In a lot of cases actually,

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some enterprises may
actually have their own apps,

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so they have a different market.

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00:15:39,990 --> 00:15:43,416
So, it's not only because a
device actually has to be rooted

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00:15:43,416 --> 00:15:46,600
and you want to get a free
game from some other market,

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00:15:46,600 --> 00:15:51,010
but in some cases actually
are some legitimate stores

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00:15:52,070 --> 00:15:53,840
or alternate markets

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00:15:53,840 --> 00:15:56,710
that applications actually
need to be signed,

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00:15:56,710 --> 00:15:59,190
and those are actually
signed with a third-party

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00:15:59,190 --> 00:16:01,573
or self-signed certificate.

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00:16:02,530 --> 00:16:04,700
Now, applications do not have to be signed

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by a Central Authority,

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00:16:06,450 --> 00:16:09,420
and Android currently does not perform

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00:16:09,420 --> 00:16:12,150
any Certificate Authority verification

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00:16:12,150 --> 00:16:14,370
for application certificates.

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00:16:14,370 --> 00:16:18,310
And that can be actually
huge in the case of security

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00:16:18,310 --> 00:16:21,180
because it may actually
lead to a security problems,

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00:16:21,180 --> 00:16:25,380
if you actually don't
verify the CA verification.

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00:16:25,380 --> 00:16:28,220
Of course, it's a little
bit different to scale

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00:16:28,220 --> 00:16:30,150
whenever you provide the operating system

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00:16:30,150 --> 00:16:32,920
and you have many, many
different implementers

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00:16:32,920 --> 00:16:35,740
in comparison to, let's say, Apple,

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00:16:35,740 --> 00:16:37,729
that they actually control all the devices

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00:16:37,729 --> 00:16:42,729
and it's not like Apple iOS
is running in other vendors,

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00:16:43,890 --> 00:16:45,493
in other vendors' hardware.