Can a tag be cloned without touching it?
Only by getting a reader within a couple of centimetres of it and keeping it there while the exchange completes. A tag has no power of its own, so it must sit inside the reader's field the whole time. That rules out the scenario people picture, of a copy taken while walking past.
The tag has to be powered
A tag contains no battery. Every read starts with the reader creating a field, and the tag drawing enough energy from it to run.
That energy falls away sharply with distance. The working range is not a matter of signal quality that better equipment improves without limit; it is a matter of whether the chip receives enough power to operate at all.
Below that threshold the tag does not answer weakly. It does not answer.
And powered for the whole exchange
A read is not an instant. The reader has to detect the tag, select it, and then transfer the content, and the tag must remain powered throughout.
So the attacker does not need a fleeting moment of proximity. They need sustained proximity, held steady, while nothing moves.
That is the detail that collapses most imagined scenarios. Brushing past somebody in a corridor does not do it, and neither does a crowded train.
What a bigger antenna buys
Larger antennas and more powerful readers exist, and they do extend the working distance. Nobody honest claims otherwise.
What they do not do is change the shape of the problem. The reader remains an object that has to be brought near, and it becomes larger and more conspicuous as its range grows.
An adversary willing to carry a briefcase sized antenna and stand beside you has, at that point, an easier route: taking the card.
What this means in practice
For a tag in a wallet, in a bag, or on a wall, the realistic threat is somebody who handles it, not somebody who passes it.
The countermeasure that follows is unglamorous: know where your tags are, and do not leave a tag that matters somewhere a stranger can hold something against it for several seconds unobserved.
Shielding materials exist and work, and they address a threat that was already small. Judge whether the inconvenience is worth it in your case rather than buying reflexively.
And note that none of this applies to the address behind the tag, which is reachable by anybody at any distance once it is known.
Frequently asked questions
Could someone read my tag as they walk past?
No. The tag must stay inside the reader's field for the whole exchange, which needs sustained proximity rather than a moment.
Do more powerful readers change this?
They extend the range, and they get larger and more conspicuous as they do. The reader still has to be brought near.
Is a shielded wallet worth buying?
It works, against a threat that was already small. Decide by the value of what you carry rather than by reflex.
Does distance protect the page behind the tag?
No. Once the address is known it can be visited from anywhere. Only the tag itself is protected by proximity.