It would be possible for old links where the signal is converted back to an electric signal, cleaned and regenerated every 200km of so. But it isn't possible for recent links where the amplification is done using a erbium doped fiber. The signal never leaves the fiber.
I can see two ways of doing it without cutting the fiber.
First, when you bend an optical fiber, some light gets out. You just have to find a detector sensible enough to detect this light.
Second, you can place a fiber parrallel and really close (touching) to the transmission fiber and their will be some coupling of light in this second fiber.
These two ways reduce a little bit the output of the fiber but could easily go unnoticed.
I don't know about other online banking systems, but the one used by my bank isn't totally automated. Accounts sold and other informations are automaticaly updated from the internal network to the online banking network, but transactions made using the online banking have to be confirmed by an employee to go from the online banking network to the internal network. If those employees are well trained, they will probably detect suspect transactions.
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It would be possible for old links where the signal is converted back to an electric signal, cleaned and regenerated every 200km of so. But it isn't possible for recent links where the amplification is done using a erbium doped fiber. The signal never leaves the fiber.
I can see two ways of doing it without cutting the fiber. First, when you bend an optical fiber, some light gets out. You just have to find a detector sensible enough to detect this light. Second, you can place a fiber parrallel and really close (touching) to the transmission fiber and their will be some coupling of light in this second fiber. These two ways reduce a little bit the output of the fiber but could easily go unnoticed.
I don't know about other online banking systems, but the one used by my bank isn't totally automated. Accounts sold and other informations are automaticaly updated from the internal network to the online banking network, but transactions made using the online banking have to be confirmed by an employee to go from the online banking network to the internal network. If those employees are well trained, they will probably detect suspect transactions.