I'm hearing a lot about the 'unmasking' of some of Trump's people in the news today, in relation to Susan Rice. It seems to be an American-phenomenon; we don't have a similar concept here that I'm aware of. Any chance someone could explain what it is?
So that was Trump's latest distraction. There really isn't much there and it's making noise about a minor point.
But in detail;
There are a number of ways that it is legal for the US to collect electronic surveillance (wiretaps or otherwise) against an individual. Under
FISA section 702 (which may be going away soon),
Executive Order 12333 or simply under certain justice department law enforcement warrants.
All of these have legal restrictions on who they can apply to. 12333 and 702 collection can only apply to foreign nationals outside the US, while warrants (FISA 702 or general DOJ) only apply to the named entities in the warrants and require a judge (either FISC or DOJ) to sign off on the evidence justifying the collection.
But the nature of surveillance means a lot of what you capture is the individual talking to other people not legally permitted to be spied on. This is known as incidental collection.
The identities of people incidentally spied on in this way must be protected through masking; censoring of any reports based on that intelligence as well as any transcripts released.
Masking, as a rule, should completely hide the identity of such people and so any potentially identifying information is stripped. This can greatly reduce the value of such intelligence if the conversations are relevant and makes any released reports look heavily censored.
It goes without saying that these identities are not always irrelevant. If you are spying on a known terrorist and they are making a dozen calls a day to a guy who just bought a gun store in Dallas that might be relevant to your investigation. The agents who originally collect this information have some leeway in how to act on such information. Certainly further warrants can be sought on the basis of incidental collection, sometimes under a different agency and enforcement power than the original (so 702 overseas collection leading to a DOJ warrant against a US individual). In some cases individuals can be completely unmasked in the original report where their identity is deemed essential to understanding the intelligence gathered. So, say, knowing which administration official has been talking to a known Russian agent in the course of an ongoing investigation into major crimes.
Incidental collection can also be used to
warn targets of attacks, although in such cases the FBI themselves wouldn't unmask them outside of the warning phone call.
In this case it would appear that Rice was handed intelligence reports that incidentally involved Trump transition team members.
She requested that they be unmasked to better understand the context. This is pretty much normal behaviour in the course of such an investigation. Also noteworthy that if they had been fully masked then she wouldn't know who it was she was asking to be unmasked, then it turns out to be a Trump official...
There are also obviously levels of unmasking. You could reveal the full identity or just show some context to the conversations. It's not clear exactly what was requested or done in this case and there are conflicting reports. Of course, Trump could simply declassify the materials if he wished, but seems to be relying on secondary reporting of journalists.