Let’s explore legitimate (and not-so-legitimate) reasons:
Over the years, various open-source and commercial toolsets have been developed to demonstrate or exploit these flaws: gsm crack tool
For engineers and security enthusiasts who want to understand why cracking is now nearly impossible: extract the Ki and IMSI
Between 2015 and 2018, a website called gsmcracktool(dot)com claimed to offer a one-click solution to crack any SIM. The download was a 2 MB executable file. gsm crack tool
These tools read the data from a legitimate SIM card, extract the Ki and IMSI, and write that data onto a blank programmable SIM card (like a Silvercard or USIM card). Popular historical tools include:
