There is so much fraud with internet CC's that more & more companies require you to provide the CID number. As Elbert stated, It's to prove you are who you say you are. (And the merchant gets a small break on his transaction fees) Get used to it gang. And, if it gets rubbed off ( typical) you cannot call the issuer and find out what is is. They force you to visit office or issue a new card.

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But then what do I know, I am but a mere caveman