Tens of thousands of computers hit by global cyberattack

Ransomware has spread throughout four continents and affected networks of several major U.S. companies.
2:04 | 06/28/17

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Transcript for Tens of thousands of computers hit by global cyberattack
We move to that massive global signary tack. It has hit hospital, bank, government agent cyst and companies from Ukraine to Europe, parts of the U.S. As well. The hackers are seeking ransom to release crucial data and our chief investigative correspondent Brian Ross has a major new development. Good morning. Reporter: Good morning. Right now the attacks continue but this morning, researchers say they may have discovered a kind of kill switch that could stop or at least slow its spread. Hospitals outside Pittsburgh in beaver, Pennsylvania, were among the targets where doctors could not access patients' medical records. She called and said surgery was canceled because a computer was down. Reporter: Other targets in the U.S. Include Merck pharmaceutical in New Jersey, even the company that makes oreo cookies may have been hit as well as the computers and phones at this Washington law firm which warned its lawyers as they entered the lobby. You can't read any e-mails. You can't read any files. Basically your computer becomes a brick. Reporter: It first surfaced in Ukraine shutting down everything from grocery stores to atm machine, power grids and airports. The thousands of targets all received this ominous message in English on their screens, your files are no longer accessible. Nobody can recover your files without our decryption service, send $300 worth of Bitcoin. Sometimes if you pay you get your data back. Sometimes they just take your money and move on. Reporter: It bears great similarities to a scheme last month that hit British hospitals particularly hard. But that attack later linked to North Korea was stopped when cybersecurity experts discovered a kind of kill switch. This morning computer experts are trying to activate a new kill switch, a vaccine to protect individual computers. What can L of us do? Microsoft has put out a patch or a fix. This attacks vulnerabilities in the windows operating system so download any upgrades from Microsoft. Obviously a lot of people have not done that. Okay, Brian Ross, thanks very

This transcript has been automatically generated and may not be 100% accurate.

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