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Consider the following two sentences, dealing with a singular "ISP":
(1) The virus penetrated the Internet Service Provider's (ISP)'s firewall.
(2) The virus penetrated the Internet Service Provider (ISP)'s firewall.
The subtle difference is that (1) has a possessive apostrophe both on the term and its abbreviation, whereas (2) only has it on the abbreviation. Which of the above two is more commonly preferred?