2 Factor Authentication has grown a lot over the past year, and the sense of security is at an all time high! Who can get to my bitcoins, altcoins, email etc now!? I have my phone right here, and I have a strong password. I'm safe! ( ... )
So the hack that people has been doing is fairly simple, If you have some experience prank-calling and keeping a straight face, you could great at social engineering. You simply call up the phone provider of the target, convince some stressed out girl/guy at the mobile-company that you need a new SIM-card for your phone (Fill in with a good story).
When someone has your SIM-card they can, for example, bypass 2FA with a SMS-login for example.
Remember, being part of the crypto-sphere can attract people who think you have a lot of crypto-cash for example, and will try to hack you. (or they see it here in the wallet) And not just to steal your coins/steem, but to maybe black-mail you into paying coins because the hacker found nudes of your wife or a draft to your boss quitting your job.
Stay safe and hold on to your SIM-cards fellow Steemians!