A global computer hack, using a cyberweapon developed by the National Security Agency, has disrupted hospitals, universities, government offices, gas stations, ATM machines and more than 200,000 computers worldwide—and it’s expected to grow worse as people return to work this morning. On Friday, the cyberattacks began to ripple through more than 150 countries, locking medical workers out of the computer systems at dozens of British and Indonesian hospitals, disrupting train schedules in Germany, preventing Chinese students from accessing their final papers and freezing government computers from Russia’s Interior Ministry to police stations in India. Experts say it’s the first time a cyberweapon developed by the NSA has been stolen and released by hackers. The cyberweapon exploits weaknesses in Microsoft software. It appears the U.S. government knew for years about this weakness in the software but only told Microsoft about the vulnerability recently, meaning Microsoft had little time to fix the problem and for software users worldwide to update their systems. The cyberweapon is transmitted by email and then encrypts a computer, locking people out of their data and then threatening to destroy it unless a ransom is paid. On Sunday, Microsoft President Brad Smith confirmed the cyberweapon used in the attack was developed by the NSA, writing, “Finally, this attack provides yet another example of why the stockpiling of vulnerabilities by governments is such a problem. … An equivalent scenario with conventional weapons would be the U.S. military having some of its Tomahawk missiles stolen.” NSA whistleblower Edward Snowden tweeted, “Despite warnings, @NSAGov built dangerous attack tools that could target Western software. Today we see the cost.”