1#Security Enhancements in Android 4.2 2 3Android provides a multi-layered security model described in the [Android 4Security Overview](index.html). Each update to Android includes dozens of 5security enhancements to protect users. The following are some of the security 6enhancements introduced in Android 4.2: 7 8+ **Application verification.** Users can choose to enable “Verify Apps" and 9have applications screened by an application verifier, prior to installation. 10App verification can alert the user if they try to install an app that might be 11harmful; if an application is especially bad, it can block installation. 12 13+ **More control of premium SMS.** Android will provide a notification if an 14application attempts to send SMS to a short code that uses premium services 15which might cause additional charges. The user can choose whether to allow the 16application to send the message or block it. 17 18+ **Always-on VPN.** VPN can be configured so that applications will not have 19access to the network until a VPN connection is established. This prevents 20applications from sending data across other networks. 21 22+ **Certificate Pinning.** The Android core libraries now support 23[certificate pinning](https://developer.android.com/reference/android/net/http/X509TrustManagerExtensions.html). Pinned domains will receive a certificate validation 24failure if the certificate does not chain to a set of expected certificates. 25This protects against possible compromise of Certificate Authorities. 26 27+ **Improved display of Android permissions.** Permissions have been organized 28into groups that are more easily understood by users. During review of the 29permissions, the user can click on the permission to see more detailed 30information about the permission. 31 32+ **installd hardening.** The installd daemon does not run as the root user, 33reducing potential attack surface for root privilege escalation. 34 35+ **init script hardening.** init scripts now apply O_NOFOLLOW semantics to 36prevent symlink related attacks. 37 38+ **FORTIFY_SOURCE.** Android now implements FORTIFY_SOURCE. This is used by 39system libraries and applications to prevent memory corruption. 40 41+ **ContentProvider default configuration.** Applications which target API 42level 17 will have "export" set to "false" by default for each 43[ContentProvider](https://developer.android.com/reference/android/content/ContentProvider.html), 44reducing default attack surface for applications. 45 46+ **Cryptography.** Modified the default implementations of SecureRandom and 47Cipher.RSA to use OpenSSL. Added SSL Socket support for TLSv1.1 and TLSv1.2 48using OpenSSL 1.0.1 49 50+ **Security Fixes.** Upgraded open source libraries with security fixes include 51WebKit, libpng, OpenSSL, and LibXML. Android 4.2 also includes fixes for 52Android-specific vulnerabilities. Information about these vulnerabilities has 53been provided to Open Handset Alliance members and fixes are available in 54Android Open Source Project. To improve security, some devices with earlier 55versions of Android may also include these fixes. 56