  We present the results of the first large-scale study into Android markets
that offer modified or modded apps: apps whose features and functionality have
been altered by a third-party. We analyse over 146k (thousand) apps obtained
from 13 of the most popular modded app markets. Around 90% of apps we collect
are altered in some way when compared to the official counterparts on Google
Play. Modifications include games cheats, such as infinite coins or lives;
mainstream apps with premium features provided for free; and apps with modified
advertising identifiers or excluded ads. We find the original app developers
lose significant potential revenue due to: the provision of paid for apps for
free (around 5% of the apps across all markets); the free availability of
premium features that require payment in the official app; and modified
advertising identifiers. While some modded apps have all trackers and ads
removed (3%), in general, the installation of these apps is significantly more
risky for the user than the official version: modded apps are ten times more
likely to be marked as malicious and often request additional permissions.
