Why different Users for different services - SQL Server 2008

i am preparing for Microsoft exam 70-432 SQL Server 2008 . In the book i read, its highly recommended that you use separate log-in for each SQL Service. But i am unable to unde开发者_开发问答rstand what is a benefit in using separate USER?

Please let me know if anyone has an idea about this.

Regards, fayalif

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The benefit is that if somehow someone manages to take control of one of the services he will not have access to the other ones.

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What Giorgi said and that the different services require different rights.

By using different accounts these individual accounts have as little rights as possible. Combining these accounts by using one account a malicious user could obtain enough rights to do damage.