Because it uses a very flexible model for applications, Android apps can do things that cannot be done on the other platforms. A user is notified what an application will be allowed to do at install time, and can choose to install it or not. Once installed, third party apps can (if authorized at install time) read and send messages, make and receive calls, access the internet and turn the microphone or camera on and off.
Because users are not very good at either reading or understanding the implications of these permissions, Android applications have been caught sending and receiving premium rate calls and messages, recording users keystrokes or sounds, tracking user locations, or even containing botnet-style malware as might be found on a desktop machine. There are quite a few third party solutions available that purport to secure your device, but their effectiveness is in many cases under question.
The flexibility of Android makes it a great choice for a highly capable user, but it can require quite a bit of knowledge to keep secure in the long run--often this will require that users root the device and install their own custom updates directly if the carrier does not provide them. Clearly not for the technical novice!
While Android is taking the biggest bite out of the consumer market, Blackberry has been very much the jewel of the business world. With its users being likened to drug addicts for their dependence upon the device, RIM's Blackbery devices have earned the designation Crackberry. Even President Obama couldn't part with his device, reportedly much to the irritation of the Secret Service and delight of Research in Motion.
Security and control are some of the main selling points of Blackberry, with the ability to completely encrypt data, tightly control what is done with the device, restrict what individual applications can and cannot do, require tunneling of any and all internet traffic through the company's servers, control apps and much more. The downside is that this control comes at a cost, and the ease of management to keep your device secure can be time consuming for a non-enterprise user.
Blackberry App World, the source for third party applications, offers a degree of review over all submissions. However, source code is not reviewed by RIM, and only so much can be understood of application behavior. While Blackberry hasn't been targeted by nearly the same amount of spyware or malware as Android, there have been instances of nefarious applications and spyware-trojaned carrier updates.
The ability to lock down and secure Blackberry devices is definitely a plus, but because much of it was designed with enterprises in mind it can get a bit complex for a standard user unless they are careful. The release of more consumer oriented devices based upon Blackberry 10 shows promise, but as it is unreleased at present, this one should stay on hold for individual users for now.
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