  We describe a cheating strategy enabled by the features of massive open
online courses (MOOCs) and detectable by virtue of the sophisticated data
systems that MOOCs provide. The strategy, Copying Answers using Multiple
Existences Online (CAMEO), involves a user who gathers solutions to assessment
questions using a "harvester" account and then submits correct answers using a
separate "master" account. We use "clickstream" learner data to detect CAMEO
use among 1.9 million course participants in 115 MOOCs from two universities.
Using conservative thresholds, we estimate CAMEO prevalence at 1,237
certificates, accounting for 1.3% of the certificates in the 69 MOOCs with
CAMEO users. Among earners of 20 or more certificates, 25% have used the CAMEO
strategy. CAMEO users are more likely to be young, male, and international than
other MOOC certificate earners. We identify preventive strategies that can
decrease CAMEO rates and show evidence of their effectiveness in science
courses.
