Question: In Lawful Interception (LI) for SMS, when removing the content of an SMS message due to IRI-only interception, what happens to the non-'SMS Control' Information Elements within the TP-User-Data Header?
Option 1: They are left unchanged to maintain message integrity.
Option 2: They are removed entirely without replacement.
Option 3: They are encrypted to protect user data further.
Option 4: They are converted to a Filler Information Element.
Explanation: To ensure backwards compatibility in SMS decoding implementations while removing sensitive content, non-'SMS Control' Information Elements within the TP-User-Data Header must be converted into a neutral format. Converting them to a Filler Information Element achieves this without altering the overall length of the TP-User-Data or its Header, thus maintaining compatibility and adhering to the specified procedure for Lawful Interception.