A partir de 27 de março de 2025, recomendamos usar android-latest-release em vez de aosp-main para criar e contribuir com o AOSP. Para mais informações, consulte Mudanças no AOSP.

Esta página foi traduzida pela API Cloud Translation.

Melhorias na segurança

O Android está sempre melhorando as ofertas e as capacidades de segurança. Confira as listas de melhorias por versão no painel de navegação à esquerda.

Android 14

Cada versão do Android inclui dezenas de melhorias de segurança para proteger os usuários. Confira algumas das principais melhorias de segurança disponíveis no Android 14:

O limpador de endereços assistido por hardware (HWASan), introduzido no Android 10, é uma ferramenta de detecção de erros de memória semelhante ao AddressSanitizer. O Android 14 traz melhorias significativas para o HWASan. Saiba como ele ajuda a evitar que bugs cheguem às versões do Android, HWAddressSanitizer
No Android 14, começando por apps que compartilham dados de local com terceiros, a caixa de diálogo de permissão de execução do sistema agora inclui uma seção clicável que destaca as práticas de compartilhamento de dados do app. Isso inclui o motivo pelo qual esse app pode compartilhar dados com terceiros.
O Android 12 apresentou uma opção para desativar o suporte a 2G no nível do modem, que protege os usuários do risco de segurança inerente do modelo de segurança obsoleto do 2G. O Android 14 ativa esse recurso de segurança no Android Enterprise, introduzindo suporte para que administradores de TI restrinjam a capacidade de um dispositivo gerenciado de fazer downgrade para a conectividade 2G.
Adição de suporte para rejeitar conexões de celular com criptografia nula, garantindo que o tráfego de voz e SMS com comutação de circuitos seja sempre criptografado e protegido contra interceptação passiva over-the-air. Saiba mais sobre o programa do Android para aumentar a segurança da conectividade celular.
Adição de suporte a vários IMEIs
Desde o Android 14, o AES-HCTR2 é o modo de preferência da criptografia de nomes de arquivos para dispositivos com instruções de criptografia acelerada.
Conectividade celular
Adicionamos documentação para o Centro de segurança do Android.
Se o app for direcionado ao Android 14 e usar o carregamento de código dinâmico (DCL, na sigla em inglês), todos os arquivos carregados dinamicamente vão precisar ser marcados como somente leitura. Caso contrário, o sistema vai gerar uma exceção. Recomendamos que os apps evitem carregar código dinamicamente sempre que possível, porque isso aumenta muito o risco de comprometimento do app por injeção ou adulteração de código.

Confira as notas da versão completas do AOSP e a lista de recursos e mudanças para desenvolvedores do Android.

Android 13

Cada versão do Android inclui dezenas de melhorias de segurança para proteger os usuários. Confira algumas das principais melhorias de segurança disponíveis no Android 13:

O Android 13 agora é compatível com a apresentação de vários documentos. A nova interface de sessão de apresentação permite que um app faça uma apresentação de vários documentos, algo que não é possível com a API atual. Para mais informações, consulte Credencial de identidade.
No Android 13, as intents originadas de apps externos vão ser enviadas a um componente exportado apenas se corresponderem aos elementos de filtro de intent declarados.
A API Open Mobile (OMAPI, link em inglês) é uma API padrão usada para se comunicar com o Elemento de segurança de um dispositivo. Antes do Android 13, apenas apps e módulos de framework tinham acesso a essa interface. Ao fazer a conversão para uma interface estável do fornecedor, os módulos da HAL também podem se comunicar com os Elementos de segurança pelo serviço OMAPI. Para mais informações, consulte Interface estável do fornecedor OMAPI.
No Android 13 QPR, os UIDs compartilhados foram descontinuados. Os usuários do Android 13 ou versões mais recentes precisam incluir a linha `android:sharedUserMaxSdkVersion="32"` no manifesto. Essa entrada impede que novos usuários recebam um UID compartilhado. Para mais informações sobre UIDs, consulte Assinatura de apps.
O Android 13 adicionou suporte a primitivas criptográficas simétricas do Keystore, como AES (Advanced Encryption Standard), HMAC (Keyed-Hash Message Authentication Code) e algoritmos criptográficos assimétricos (incluindo curva elíptica, RSA2048, RSA4096 e curva 25519).
O Android 13 (nível 33 da API) e versões mais recentes oferecem suporte a uma permissão de execução para enviar notificações de um app não isentas. Isso dá aos usuários controle sobre quais notificações de permissão eles veem.
Adicionamos uma solicitação por uso para apps que solicitam acesso a todos os registros do dispositivo, permitindo que os usuários permitam ou neguem o acesso.
introduziu o Framework de virtualização do Android (AVF, na sigla em inglês), que reúne diferentes hipervisores em um framework com APIs padronizadas. Ele fornece ambientes de execução seguros e particulares para executar cargas de trabalho isoladas por hipervisor.
Introdução do Esquema de assinatura de APK v3.1 Todas as novas rotações de chaves que usam o apksigner usam o esquema de assinatura v3.1 por padrão para a rotação do Android 13 e versões mais recentes.

Confira as notas da versão completas do AOSP e a lista de recursos e mudanças para desenvolvedores do Android.

Android 12

Cada versão do Android inclui dezenas de melhorias de segurança para proteger os usuários. Confira algumas das principais melhorias de segurança disponíveis no Android 12:

O Android 12 apresenta a API BiometricManager.Strings, que fornece strings localizadas para apps que usam BiometricPrompt para autenticação. Essas strings foram criadas para serem compatíveis com dispositivos e fornecer mais especificidade sobre quais tipos de autenticação podem ser usados. O Android 12 também inclui suporte para sensores de impressão digital abaixo da tela
Adição de suporte para sensores de impressão digital abaixo da tela
Introdução à Linguagem de definição de interface do Android de impressão digital (AIDL)
Suporte para a nova AIDL de rosto
Introdução do Rust como uma linguagem para desenvolvimento de plataformas
A opção de conceder acesso apenas à localização aproximada foi adicionada
Adição de indicadores de privacidade na barra de status quando um app está usando a câmera ou o microfone
O Private Compute Core (PCC) do Android
Adição de uma opção para desativar o suporte a 2G

Android 11

Cada versão do Android inclui dezenas de melhorias de segurança para proteger os usuários. Para conferir uma lista de algumas das principais melhorias de segurança disponíveis no Android 11, consulte as Notas da versão do Android.

Android 10

Every Android release includes dozens of security enhancements to protect users. Android 10 includes several security and privacy enhancements. See the Android 10 release notes for a complete list of changes in Android 10.

Security

BoundsSanitizer

Android 10 deploys BoundsSanitizer (BoundSan) in Bluetooth and codecs. BoundSan uses UBSan's bounds sanitizer. This mitigation is enabled on a per-module level. It helps keep critical components of Android secure and shouldn't be disabled. BoundSan is enabled in the following codecs:

libFLAC
libavcdec
libavcenc
libhevcdec
libmpeg2
libopus
libvpx
libspeexresampler
libvorbisidec
libaac
libxaac

Execute-only memory

By default, executable code sections for AArch64 system binaries are marked execute-only (nonreadable) as a hardening mitigation against just-in-time code reuse attacks. Code that mixes data and code together and code that purposefully inspects these sections (without first remapping the memory segments as readable) no longer functions. Apps with a target SDK of Android 10 (API level 29 or higher) are impacted if the app attempts to read code sections of execute-only memory (XOM) enabled system libraries in memory without first marking the section as readable.

Extended access

Trust agents, the underlying mechanism used by tertiary authentication mechanisms such as Smart Lock, can only extend unlock in Android 10. Trust agents can no longer unlock a locked device and can only keep a device unlocked for a maximum of four hours.

Face authentication

Face authentication allows users to unlock their device simply by looking at the front of their device. Android 10 adds support for a new face authentication stack that can securely process camera frames, preserving security and privacy during face authentication on supported hardware. Android 10 also provides an easy way for security-compliant implementations to enable app integration for transactions such as online banking or other services.

Integer Overflow Sanitization

Android 10 enables Integer Overflow Sanitization (IntSan) in software codecs. Ensure that playback performance is acceptable for any codecs that aren't supported in the device's hardware. IntSan is enabled in the following codecs:

libFLAC
libavcdec
libavcenc
libhevcdec
libmpeg2
libopus
libvpx
libspeexresampler
libvorbisidec

Modular system components

Android 10 modularizes some Android system components and enables them to be updated outside of the normal Android release cycle. Some modules include:

OEMCrypto

Android 10 uses OEMCrypto API version 15.

Scudo

Scudo is a dynamic user-mode memory allocator designed to be more resilient against heap-related vulnerabilities. It provides the standard C allocation and deallocation primitives, as well as the C++ primitives.

ShadowCallStack

ShadowCallStack (SCS) is an LLVM instrumentation mode that protects against return address overwrites (like stack buffer overflows) by saving a function's return address to a separately allocated ShadowCallStack instance in the function prolog of nonleaf functions and loading the return address from the ShadowCallStack instance in the function epilog.

WPA3 and Wi-Fi Enhanced Open

Android 10 adds support for the Wi-Fi Protected Access 3 (WPA3) and Wi-Fi Enhanced Open security standards to provide better privacy and robustness against known attacks.

Privacy

App access when targeting Android 9 or lower

If your app runs on Android 10 or higher but targets Android 9 (API level 28) or lower, the platform applies the following behavior:

If your app declares a <uses-permission> element for either ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION, the system automatically adds a <uses-permission> element for ACCESS_BACKGROUND_LOCATION during installation.
If your app requests either ACCESS_FINE_LOCATION or ACCESS_COARSE_LOCATION, the system automatically adds ACCESS_BACKGROUND_LOCATION to the request.

Background activity restrictions

Starting in Android 10, the system places restrictions on starting activities from the background. This behavior change helps minimize interruptions for the user and keeps the user more in control of what's shown on their screen. As long as your app starts activities as a direct result of user interaction, your app most likely isn't affected by these restrictions.
To learn more about the recommended alternative to starting activities from the background, see the guide on how to alert users of time-sensitive events in your app.

Camera metadata

Android 10 changes the breadth of information that the getCameraCharacteristics() method returns by default. In particular, your app must have the CAMERA permission in order to access potentially device-specific metadata that is included in this method's return value.
To learn more about these changes, see the section about camera fields that require permission.

Clipboard data

Unless your app is the default input method editor (IME) or is the app that currently has focus, your app cannot access clipboard data on Android 10 or higher.

Device location

To support the additional control that users have over an app's access to location information, Android 10 introduces the ACCESS_BACKGROUND_LOCATION permission.
Unlike the ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION permissions, the ACCESS_BACKGROUND_LOCATION permission only affects an app's access to location when it runs in the background. An app is considered to be accessing location in the background unless one of the following conditions is satisfied:

An activity belonging to the app is visible.
The app is running a foreground service that has declared a foreground service type of location.
To declare the foreground service type for a service in your app, set your app's targetSdkVersion or compileSdkVersion to 29 or higher. Learn more about how foreground services can continue user-initiated actions that require access to location.

External storage

By default, apps targeting Android 10 and higher are given scoped access into external storage, or scoped storage. Such apps can see the following types of files within an external storage device without needing to request any storage-related user permissions:

Files in the app-specific directory, accessed using getExternalFilesDir().
Photos, videos, and audio clips that the app created from the media store.

To learn more about scoped storage, as well as how to share, access, and modify files that are saved on external storage devices, see the guides on how to manage files in external storage and access and modify media files.

MAC address randomization

On devices that run Android 10 or higher, the system transmits randomized MAC addresses by default.
If your app handles an enterprise use case, the platform provides APIs for several operations related to MAC addresses:

Obtain randomized MAC address: Device owner apps and profile owner apps can retrieve the randomized MAC address assigned to a specific network by calling getRandomizedMacAddress().
Obtain actual, factory MAC address: Device owner apps can retrieve a device's actual hardware MAC address by calling getWifiMacAddress(). This method is useful for tracking fleets of devices.

Non-resettable device identifiers

Starting in Android 10, apps must have the READ_PRIVILEGED_PHONE_STATE privileged permission in order to access the device's non-resettable identifiers, which include both IMEI and serial number.

Build
- getSerial()
TelephonyManager
- getImei()
- getDeviceId()
- getMeid()
- getSimSerialNumber()
- getSubscriberId()

If your app doesn't have the permission and you try asking for information about non-resettable identifiers anyway, the platform's response varies based on target SDK version:

If your app targets Android 10 or higher, a SecurityException occurs.
If your app targets Android 9 (API level 28) or lower, the method returns null or placeholder data if the app has the READ_PHONE_STATE permission. Otherwise, a SecurityException occurs.

Physical activity recognition

Android 10 introduces the android.permission.ACTIVITY_RECOGNITION runtime permission for apps that need to detect the user's step count or classify the user's physical activity, such as walking, biking, or moving in a vehicle. This is designed to give users visibility of how device sensor data is used in Settings.
Some libraries within Google Play services, such as the Activity Recognition API and the Google Fit API, don't provide results unless the user has granted your app this permission.
The only built-in sensors on the device that require you to declare this permission are the step counter and step detector sensors.
If your app targets Android 9 (API level 28) or lower, the system auto-grants the android.permission.ACTIVITY_RECOGNITION permission to your app, as needed, if your app satisfies each of the following conditions:

The manifest file includes the com.google.android.gms.permission.ACTIVITY_RECOGNITION permission.
The manifest file doesn't include the android.permission.ACTIVITY_RECOGNITION permission.

If the system-auto grants the android.permission.ACTIVITY_RECOGNITION permission, your app retains the permission after you update your app to target Android 10. However, the user can revoke this permission at any time in system settings.

/proc/net filesystem restrictions

On devices that run Android 10 or higher, apps cannot access /proc/net, which includes information about a device's network state. Apps that need access to this information, such as VPNs, should use the NetworkStatsManager or ConnectivityManager class.

Permission groups removed from UI

As of Android 10, apps cannot look up how permissions are grouped in the UI.

Removal of contacts affinity

Starting in Android 10, the platform doesn't keep track of contacts affinity information. As a result, if your app conducts a search on the user's contacts, the results aren't ordered by frequency of interaction.
The guide about ContactsProvider contains a notice describing the specific fields and methods that are obsolete on all devices starting in Android 10.

Restricted access to screen contents

To protect users' screen contents, Android 10 prevents silent access to the device's screen contents by changing the scope of the READ_FRAME_BUFFER, CAPTURE_VIDEO_OUTPUT, and CAPTURE_SECURE_VIDEO_OUTPUT permissions. As of Android 10, these permissions are signature-access only.
Apps that need to access the device's screen contents should use the MediaProjection API, which displays a prompt asking the user to provide consent.

USB device serial number

If your app targets Android 10 or higher, your app cannot read the serial number until the user has granted your app permission to access the USB device or accessory.
To learn more about working with USB devices, see the guide on how to configure USB hosts.

Wi-Fi

Apps targeting Android 10 or higher cannot enable or disable Wi-Fi. The WifiManager.setWifiEnabled() method always returns false.
If you need to prompt users to enable and disable Wi-Fi, use a settings panel.

Restrictions on direct access to configured Wi-Fi networks

To protect user privacy, manual configuration of the list of Wi-Fi networks is restricted to system apps and device policy controllers (DPCs). A given DPC can be either the device owner or the profile owner.
If your app targets Android 10 or higher, and it isn't a system app or a DPC, then the following methods don't return useful data:

The getConfiguredNetworks() method always returns an empty list.
Each network operation method that returns an integer value—addNetwork() and updateNetwork()—always returns -1.
Each network operation that returns a boolean value—removeNetwork(), reassociate(), enableNetwork(), disableNetwork(), reconnect(), and disconnect()—always returns false.

Android 9

Android 8

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 8.0:

Encryption. Added support to evict key in work profile.
Verified Boot. Added Android Verified Boot (AVB). Verified Boot codebase supporting rollback protection for use in boot loaders added to AOSP. Recommend bootloader support for rollback protection for the HLOS. Recommend boot loaders can only be unlocked by user physically interacting with the device.
Lock screen. Added support for using tamper-resistant hardware to verify lock screen credential.
KeyStore. Required key attestation for all devices that ship with Android 8.0+. Added ID attestation support to improve Zero Touch Enrollment.
Sandboxing. More tightly sandboxed many components using Project Treble's standard interface between framework and device-specific components. Applied seccomp filtering to all untrusted apps to reduce the kernel's attack surface. WebView is now run in an isolated process with very limited access to the rest of the system.
Kernel hardening. Implemented hardened usercopy, PAN emulation, read-only after init, and KASLR.
Userspace hardening. Implemented CFI for the media stack. App overlays can no longer cover system-critical windows and users have a way to dismiss them.
Streaming OS update. Enabled updates on devices that are are low on disk space.
Install unknown apps. Users must grant permission to install apps from a source that isn't a first-party app store.
Privacy. Android ID (SSAID) has a different value for each app and each user on the device. For web browser apps, Widevine Client ID returns a different value for each app package name and web origin. net.hostname is now empty and the dhcp client no longer sends a hostname. android.os.Build.SERIAL has been replaced with the Build.SERIAL API which is protected behind a user-controlled permission. Improved MAC address randomization in some chipsets.

Android 7

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 7.0:

File-based encryption. Encrypting at the file level, instead of encrypting the entire storage area as a single unit, better isolates and protects individual users and profiles (such as personal and work) on a device.
Direct Boot. Enabled by file-based encryption, Direct Boot allows certain apps such as alarm clock and accessibility features to run when device is powered on but not unlocked.
Verified Boot. Verified Boot is now strictly enforced to prevent compromised devices from booting; it supports error correction to improve reliability against non-malicious data corruption.
SELinux. Updated SELinux configuration and increased seccomp coverage further locks down the Application Sandbox and reduces attack surface.
Library load-order randomization and improved ASLR. Increased randomness makes some code-reuse attacks less reliable.
Kernel hardening. Added additional memory protection for newer kernels by marking portions of kernel memory as read-only, restricting kernel access to userspace addresses and further reducing the existing attack surface.
APK signature scheme v2. Introduced a whole-file signature scheme that improves verification speed and strengthens integrity guarantees.
Trusted CA store. To make it easier for apps to control access to their secure network traffic, user-installed certificate authorities and those installed through Device Admin APIs are no longer trusted by default for apps targeting API Level 24+. Additionally, all new Android devices must ship with the same trusted CA store.
Network Security Config. Configure network security and TLS through a declarative configuration file.

Android 6

Cada versão do Android inclui dezenas de melhorias de segurança para proteger os usuários. Confira algumas das principais melhorias de segurança disponíveis no Android 6.0:

Permissões de tempo de execução. Os apps solicitam permissões no momento da execução em vez de serem concedidas no momento da instalação. Os usuários podem ativar e desativar as permissões para apps do M e anteriores.
Inicialização verificada. Um conjunto de verificações criptográficas do software do sistema é realizado antes da execução para garantir que o smartphone esteja saudável desde o carregador de inicialização até o sistema operacional.
Segurança isolada por hardware. Nova camada de abstração de hardware (HAL, na sigla em inglês) usada pela API de impressão digital, tela de bloqueio, criptografia de dispositivo e certificados do cliente para proteger chaves contra comprometimento do kernel e/ou ataques físicos locais
Impressões digitais. Agora é possível desbloquear os dispositivos com apenas um toque. Os desenvolvedores também podem aproveitar as novas APIs para usar impressões digitais para bloquear e desbloquear chaves de criptografia.
Adoção de cartão SD. A mídia removível pode ser adotada por um dispositivo e expandir o armazenamento disponível para dados locais do app, fotos, vídeos etc., mas ainda ser protegida por criptografia em nível de bloco.
Tráfego de texto não criptografado. Os desenvolvedores podem usar um novo StrictMode para garantir que o app não use texto não criptografado.
Aumento da proteção do sistema. O aumento da proteção do sistema por meio de políticas aplicadas pelo SELinux. Isso oferece um melhor isolamento entre usuários, filtragem IOCTL, redução da ameaça de serviços expostos, maior restrição de domínios SELinux e acesso /proc extremamente limitado.
Controle de acesso USB:os usuários precisam confirmar para permitir o acesso USB a arquivos, armazenamento ou outras funcionalidades no smartphone. O padrão agora é somente cobrança, com acesso ao armazenamento que exige a aprovação explícita do usuário.

Android 5

5.0

Every Android release includes dozens of security enhancements to protect users. Here are some of the major security enhancements available in Android 5.0:

Encrypted by default. On devices that ship with L out-of-the-box, full disk encryption is enabled by default to improve protection of data on lost or stolen devices. Devices that update to L can be encrypted in Settings > Security .
Improved full disk encryption. The user password is protected against brute-force attacks using scrypt and, where available, the key is bound to the hardware keystore to prevent off-device attacks. As always, the Android screen lock secret and the device encryption key are not sent off the device or exposed to any application.
Android sandbox reinforced with SELinux . Android now requires SELinux in enforcing mode for all domains. SELinux is a mandatory access control (MAC) system in the Linux kernel used to augment the existing discretionary access control (DAC) security model. This new layer provides additional protection against potential security vulnerabilities.
Smart Lock. Android now includes trustlets that provide more flexibility for unlocking devices. For example, trustlets can allow devices to be unlocked automatically when close to another trusted device (through NFC, Bluetooth) or being used by someone with a trusted face.
Multi user, restricted profile, and guest modes for phones and tablets. Android now provides for multiple users on phones and includes a guest mode that can be used to provide easy temporary access to your device without granting access to your data and apps.
Updates to WebView without OTA. WebView can now be updated independent of the framework and without a system OTA. This allows for faster response to potential security issues in WebView.
Updated cryptography for HTTPS and TLS/SSL. TLSv1.2 and TLSv1.1 is now enabled, Forward Secrecy is now preferred, AES-GCM is now enabled, and weak cipher suites (MD5, 3DES, and export cipher suites) are now disabled. See https://developer.android.com/reference/javax/net/ssl/SSLSocket.html for more details.
non-PIE linker support removed. Android now requires all dynamically linked executables to support PIE (position-independent executables). This enhances Android's address space layout randomization (ASLR) implementation.
FORTIFY_SOURCE improvements. The following libc functions now implement FORTIFY_SOURCE protections: stpcpy(), stpncpy(), read(), recvfrom(), FD_CLR(), FD_SET(), and FD_ISSET(). This provides protection against memory-corruption vulnerabilities involving those functions.
Security Fixes. Android 5.0 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members, and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Android 4 e versões anteriores

Cada versão do Android inclui dezenas de melhorias de segurança para proteger os usuários. Confira a seguir algumas das melhorias de segurança disponíveis no Android 4.4:

Sandbox do Android reforçado com o SELinux. O Android agora usa o SELinux no modo de restrição. O SELinux é um sistema de controle de acesso obrigatório (MAC) no kernel do Linux usado para aumentar o modelo de segurança baseado em controle de acesso discricionário (DAC). Isso oferece proteção extra contra possíveis vulnerabilidades de segurança.
VPN por usuário. Em dispositivos multiusuários, as VPNs agora são aplicadas por usuário. Isso permite que um usuário roteie todo o tráfego de rede por uma VPN sem afetar outros usuários no dispositivo.
Suporte ao provedor ECDSA no AndroidKeyStore. O Android agora tem um provedor de keystore que permite o uso de algoritmos ECDSA e DSA.
Avisos de monitoramento de dispositivos. O Android mostra um aviso aos usuários se algum certificado tiver sido adicionado à loja de certificados do dispositivo que permita o monitoramento do tráfego de rede criptografado.
FORTIFY_SOURCE. O Android agora oferece suporte ao nível 2 do FORTIFY_SOURCE, e todo o código é compilado com essas proteções. O FORTIFY_SOURCE foi aprimorado para funcionar com clang.
Fixação de certificados. O Android 4.4 detecta e impede o uso de certificados fraudulentos do Google usados em comunicações SSL/TLS seguras.
Correções de segurança. O Android 4.4 também inclui correções de vulnerabilidades específicas do Android. Foram fornecidas informações sobre essas vulnerabilidades aos membros do Open Handset Alliance, e as correções estão disponíveis no Android Open Source Project. Para melhorar a segurança, alguns dispositivos com versões anteriores do Android também podem incluir essas correções.

Every Android release includes dozens of security enhancements to protect users. The following are some of the security enhancements available in Android 4.3:

Android sandbox reinforced with SELinux. This release strengthens the Android sandbox using the SELinux mandatory access control system (MAC) in the Linux kernel. SELinux reinforcement is invisible to users and developers, and adds robustness to the existing Android security model while maintaining compatibility with existing apps. To ensure continued compatibility this release allows the use of SELinux in a permissive mode. This mode logs any policy violations, but will not break apps or affect system behavior.
No setuid or setgid programs. Added support for filesystem capabilities to Android system files and removed all setuid or setgid programs. This reduces root attack surface and the likelihood of potential security vulnerabilities.
ADB authentication. Starting in Android 4.2.2, connections to ADB are authenticated with an RSA keypair. This prevents unauthorized use of ADB where the attacker has physical access to a device.
Restrict Setuid from Android Apps. The /system partition is now mounted nosuid for zygote-spawned processes, preventing Android apps from executing setuid programs. This reduces root attack surface and the likelihood of potential security vulnerabilities.
Capability bounding. Android zygote and ADB now use prctl(PR_CAPBSET_DROP) to drop unnecessary capabilities prior to executing apps. This prevents Android apps and apps launched from the shell from acquiring privileged capabilities.
AndroidKeyStore Provider. Android now has a keystore provider that allows apps to create exclusive use keys. This provides apps with an API to create or store private keys that cannot be used by other apps.
KeyChain isBoundKeyAlgorithm. Keychain API now provides a method (isBoundKeyType) that allows apps to confirm that system-wide keys are bound to a hardware root of trust for the device. This provides a place to create or store private keys that can't be exported off the device, even in the event of a root compromise.
NO_NEW_PRIVS. Android zygote now uses prctl(PR_SET_NO_NEW_PRIVS) to block addition of new privileges prior to execution app code. This prevents Android apps from performing operations that can elevate privileges through execve. (This requires Linux kernel version 3.5 or greater).
FORTIFY_SOURCE enhancements. Enabled FORTIFY_SOURCE on Android x86 and MIPS and fortified strchr(), strrchr(), strlen(), and umask() calls. This can detect potential memory corruption vulnerabilities or unterminated string constants.
Relocation protections. Enabled read only relocations (relro) for statically linked executables and removed all text relocations in Android code. This provides defense in depth against potential memory corruption vulnerabilities.
Improved EntropyMixer. EntropyMixer now writes entropy at shutdown or reboot, in addition to periodic mixing. This allows retention of all entropy generated while devices are powered on, and is especially useful for devices that are rebooted immediately after provisioning.
Security fixes. Android 4.3 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Android provides a multi-layered security model described in the Android Security Overview. Each update to Android includes dozens of security enhancements to protect users. The following are some of the security enhancements introduced in Android 4.2:

App verification: Users can choose to enable Verify Apps and have apps screened by an app verifier, prior to installation. App verification can alert the user if they try to install an app that might be harmful; if an app is especially bad, it can block installation.
More control of premium SMS: Android provides a notification if an app attempts to send SMS to a short code that uses premium services that might cause additional charges. The user can choose whether to allow the app to send the message or block it.
Always-on VPN: VPN can be configured so that apps won't have access to the network until a VPN connection is established. This prevents apps from sending data across other networks.
Certificate pinning: The Android core libraries now support certificate pinning. Pinned domains receive a certificate validation failure if the certificate doesn't chain to a set of expected certificates. This protects against possible compromise of certificate authorities.
Improved display of Android permissions: Permissions are organized into groups that are more easily understood by users. During review of the permissions, the user can click on the permission to see more detailed information about the permission.
installd hardening: The installd daemon does not run as the root user, reducing potential attack surface for root privilege escalation.
init script hardening: init scripts now apply O_NOFOLLOW semantics to prevent symlink related attacks.
FORTIFY_SOURCE: Android now implements FORTIFY_SOURCE. This is used by system libraries and apps to prevent memory corruption.
ContentProvider default configuration: Apps that target API level 17 have export set to false by default for each Content Provider, reducing default attack surface for apps.
Cryptography: Modified the default implementations of SecureRandom and Cipher.RSA to use OpenSSL. Added SSL Socket support for TLSv1.1 and TLSv1.2 using OpenSSL 1.0.1
Security fixes: Upgraded open source libraries with security fixes include WebKit, libpng, OpenSSL, and LibXML. Android 4.2 also includes fixes for Android-specific vulnerabilities. Information about these vulnerabilities has been provided to Open Handset Alliance members and fixes are available in Android Open Source Project. To improve security, some devices with earlier versions of Android may also include these fixes.

Android 1.5

ProPolice to prevent stack buffer overruns (-fstack-protector)
safe_iop to reduce integer overflows
Extensions to OpenBSD dlmalloc to prevent double free() vulnerabilities and to prevent chunk consolidation attacks. Chunk consolidation attacks are a common way to exploit heap corruption.
OpenBSD calloc to prevent integer overflows during memory allocation

Android 2.3

Format string vulnerability protections (-Wformat-security -Werror=format-security)
Hardware-based No eXecute (NX) to prevent code execution on the stack and heap
Linux mmap_min_addr to mitigate null pointer dereference privilege escalation (further enhanced in Android 4.1)

Android 4.0

Address Space Layout Randomization (ASLR) to randomize key locations in memory

Android 4.1

PIE (Position Independent Executable) support
Read-only relocations / immediate binding (-Wl,-z,relro -Wl,-z,now)
dmesg_restrict enabled (avoid leaking kernel addresses)
kptr_restrict enabled (avoid leaking kernel addresses)