Datacenters
Users of online services have all their personal data stored “in the cloud”. This “cloud”, however, is made of very physical server farms that contains extremely large amounts of data, making them great targets for tapping.
Internet Exchange Points
Internet exchange points (IX) are critical physical infrastructure through which international internet communications transit. For a country willing to wiretap such data, having IX on its ground is a great surveillance opportunity. All IX do not have the same size, and the bigger they are the more interesting they are for tapping.
Biometric Data Storage
Countries that deliver biometric passports for their citizens collect at least high-resolution face scans, usually fingerprints and even iris scans. That data is thus available to the administration.