Someone asked earlier, but I figured it's worth its own topic. Your stock carrier locked cell phone is generally fairly insecure. Obviously, the carrier can push content to your phone without your permission and remotely control it. That's fairly understood. However, even worse is that carriers tend to take their time patching known vulnerabilities in Android. At a certain point, they also stop patching a device period. Also, anyone that compromises your Google account may be able to silently install apps on your phone.
So, what are your options?
Hardware side!Well, if you don't want to go the DIY route, go with Blackphone. It has a couple subscription services, such as remote wipe and whatnot. Tech specs are on par with a Samsung Galaxy S5, and the OS is a fork of the 4.4 KitKat with some custom coding for security improvements. No google play store, so you'd probably want to install the Amazon App Store.
https://blackphone.ch/If you don't want to shell out $600, buy any phone supporting
Cyanogenmod.
You can find the list here:
http://wiki.cyanogenmod.org/w/Devicesif you want to go the extra mile, here's some hardening info:
http://www.sans.org/reading-room/whitepapers/sysadmin/securely-deploying-android-devices-33799http://forum.xda-developers.com/showthread.php?t=1954513https://blog.torproject.org/blog/mission-impossible-hardening-android-security-and-privacySoftware side!Anti-virus and security related:
http://www.av-test.org/en/home/ - Here's an independent test of numerous anti-virus, anti-malware and related applications for all platforms
DroidWall - Good Android firewall
Privacy related apps, most do not required rooted phone or cyanogenmod. All are open source, else they would not be on the list.
AES Crypt and Cryptonite are good Truecrypt alternatives for android.
KeePass is hands down the best password manager, and has clients for virtually every modern OS.
RedPhone is an encrypted SIP app, allows for secure voice chat. TextSecure is the sister app for text messages.
SSE is a general encryption app.
"The Guardian Project" is an excellent collection of privacy related apps.
https://play.google.com/store/apps/developer?id=The+Guardian+Projecthttps://guardianproject.info/