It's probably a FILTER....and the Cable Tech would use a SPECIAL TOOL to remove it. Fol. TOOL is "probably" what is used to remove it [unless it is designed to use some other type TOOL:
https://www.amazon.com/Cable-Security-Shield-Filter-Removing/dp/B00NGZGQRW
1) Filter could be a PASS BAND FILTER which only allows Internet Freqs to pass....so you can't watch regular TV...ONLY ON THAT PORT...which begs the questions as to why it wasn't attached to Splitter INPUT so it blocks watching TV on ALL ports....
OR:
2) Filter PASSES ALL CATV Freqs (up thru 860 or 1002 MHz, depending on your CATV System) and BLOCKS the higher MOCA Freqs used for Multi-Room DVR's and User Owned File Servers (i.e. PC or Network Attached Storage Device) to DLNA Player Devices (i.e. DTV and/or BD/UD-Player).
https://www.amazon.com/Cable-Security-Shield-Filter-Removing/dp/B00NGZGQRW
1) Filter could be a PASS BAND FILTER which only allows Internet Freqs to pass....so you can't watch regular TV...ONLY ON THAT PORT...which begs the questions as to why it wasn't attached to Splitter INPUT so it blocks watching TV on ALL ports....
OR:
2) Filter PASSES ALL CATV Freqs (up thru 860 or 1002 MHz, depending on your CATV System) and BLOCKS the higher MOCA Freqs used for Multi-Room DVR's and User Owned File Servers (i.e. PC or Network Attached Storage Device) to DLNA Player Devices (i.e. DTV and/or BD/UD-Player).