Recommender systems have become particularly common in e-commerce, where recommendation of items can often help a customer find what he/she is interested in and, therefore can help drive sales.
Some users in order to increase their market penetration may find it profitable to "Shill" recommender systems by lying to the systems in order to have their products recommended more often than those of their competitors.
This paper explores four open questions that may affect the effectiveness of such shilling attacks: which recommender algorithm is being used, whether the application is producing recommendations or predictions,how detectable the attacks are by the operator of the system,
and what the properties are of the items being attacked.
The questions are explored experimentally on a large data set of movie ratings. The results of the paper suggest that new ways must be used to evaluate and detect shilling attacks on recommender systems.
Read the entire article at:
http://www.grouplens.org/papers/pdf/p333-lam.pdf