[SOLVED] How does WORM microSD/SD Card work on the low level?

[dc2000]

I've been reading about Write-Once-Read-Many (WORM) microSD and SD cards. The idea is that the card will work like an old CD-R/W disk, where you can write only new files. Overwrites or any changes to existing files are not allowed. (Reads are allowed as many times as necessary.) These cards are usually used by law enforcement agencies.

Here's an example of one and here's another one.

What I'm trying to understand, is how do these cards work on the low level? In other words, how do they implement this WORM restriction?

 

[Alabalcho]

Reading how these cards operate (from your links) - there's a MCU inside to govern access, like on the smart cards (eg SIM, ATM etc).