Qualcomm BREW

BREW, or Binary Runtime Environment for Wireless, is a software development platform created by Qualcomm. The runtime was originally intended for CDMA devices, but it also can be found on GSM phones as well. Feature wise, BREW has the potential to be very powerful as it uses C/C++ for development, but the brutal DRM tactics put in place make it unsuitable for developing homebrew applications on a BREW enabled phone.

DRM
BREW has multiple application signatures in place. One signature verifies the developer of the program, another verifies that the program has passed "True Brew" testing, and these signatures are protected using the phone's ESN and MEID which is in place to prevent sideloading of BREW applications.

As of right now, there is no reliable way to exploit a BREW device to run unsigned code.

The only example of a BREW exploit is this, which appears to be a QSC60xx level exploit using modified drivers which "bypasses security features easily using a loop hole in the certificate expiration process".

(Author's note: It would be extremely impressive if someone were to get unsigned code running reliably on a BREW device.)