While cloud computing services can result in more robust, scalable and cost-effective defences against certain kinds of attacks, the European Network and Information Security Agency (ENISA) also says that cloud computing users face problems including loss of control over data, difficulties proving compliance, and additional legal risks as data moves from one legal jurisdiction to another. Other areas of concern are vendor lock-in, failure of mechanisms separating different companies, management interfaces that get accessed by hackers, data not deleted properly and malicious insiders.