The present invention generally relates to authenticating online transactions, and more specifically, to method and system for determining a potentially fraudulent online transaction request based on a risk parameter associated with a user in a networking platform such as, a social networking platform. The method comprises receiving an online transaction request from a user. Thereafter, determining the risk parameter of the user based on one or more profile parameters associated with the user or one or more peer users associated with the user in the community. Based on the risk parameter of the user the online transaction request of the user is authenticated.