The SolarWinds cyber hack gained access to then-acting DHS chief Chad Wolf's emails, sources said.

Personal data including Social Security numbers may have been stolen in the hack

Kroger Co. says it was among the multiple victims of a data breach.

Investigators in Florida say someone allegedly hacked the computer systems at a water treatment plant and tried to tamper with the water.

Officials working remotely on the presidential transition could face a serious national security risk, according to a federal intelligence analysis obtained by ABC News.

FBI warns of cyberattacks to distance learning.

Meanwhile, President Donald Trump is downplaying the attacks while casting suspicion on China instead.

Secretary Pompeo became the first U.S. official to blame Russia for the SolarWinds hack amid a low in relations as the U.S. is forced to close its last two consulates.

The security breach, which hit federal agencies including the National Nuclear Security Agency, went undetected for six months, sources told ABC News.

The FBI and U.S. Department of Homeland Security are investigating whether Russia was behind a highly-sophisticated cyber attack.

Two government officials tell ABC News that Russia is believed to be behind the cyber intrusion into the US Treasury and Commerce Departments.

Hackers apparently got into computers at the Treasury, other federal agencies.

Chain's computer networks were knocked offline by an unspecified security issue.

Authorities say the 16-year-old suspect is a student at South Miami Senior High School who allegedly confessed to eight cyber attacks that disrupted online classes during the first week of school.

New Zealand’s justice minister says the nation is confronting cyberattacks on an unprecedented scale, targeting everything from the stock market to the weather service

Garmin confirms it was victim of 'cyber attack,' but says no indication customers' data was compromised; services are expected to be restored over the coming days.

Six former eBay employees are accused of a cyberstalking campaign that authorities say targeted a couple who published a newsletter that was occasionally critical of the e-commerce site.

Japanese carmaker Honda says it has been hit by a cyberattack

The website of the Federal Depository Library Program was taken offline after the site was defaced with anti-U.S. messaging.

Foreign Ministry says its IT systems under attack, counter measures were taken.

RavnAir canceled at least a half-dozen flights at the peak of holiday travel.

The computer network that handles governmental operations for the city of New Orleans was taken offline Friday by a cyberattack, city officials say.

The FBI says cyberattacks have become common at schools.

Baltimore City officials approved using $10 million in excess revenue to cover the ongoing cost of the cyber attacks that immobilized some of the city's systems almost two months ago

Ramnicu Valcea, Romania, has earned a reputation for being a hacker breeding ground, both those who break into systems and steal information, as well as those trying to stop them.

DHS Secretary Nielsen and FBI Director Wray are testifying to the Senate today.

The city of Atlanta's computer network was targeted today by hackers demanding ransom, prompting an investigation by the FBI and the Department of Homeland Security, officials said.

The mayor of Atlanta said her city was the target of a cyberattack today.

Hackers bragged about stealing HBO programing including written material from upcoming "Game of Thrones" episode.

HBO CEO Richard Pepler told employees in an email obtained by ABC News that the hack "resulted in some stolen proprietary information, including some of our programming."

"Nightline" was on-site for the first-ever hospital cyber attack simulation designed to help doctors prepare for what cybersecurity experts say is a very real threat.

A massive cyberattack that seizes computers and demands ransom to regain access hit companies in the United States and elsewhere around the world this week.

Experts are warning that not only is the randsomware problem getting worse, but hospital computers and medical devices are vulnerable to hacking.

U.S. researcher has found a temporary "vaccine" against the attack.

A massive ransomware attack struck computers across Europe Tuesday, affecting major companies in Russia and Ukraine as well as the world's largest shipping firm, Maersk.

There was no evidence that sensitive or operational systems were breached.

Ransomware has spread throughout four continents and affected networks of several major U.S. companies.

The 'Petya' ransomware spread throughout networks in Europe and affected several major U.S. companies on Tuesday.

Researchers identified code used in WannaCry that appeared in other attacks linked to North Korea.

Researchers pointed to a piece of code suggesting North Korean involvement.

By Monday, the attack had hit more than 200 organizations in 150 countries.

Governments and companies have failed to address cybersecurity vulnerabilities.

The British National Health Service was attacked with "WannaCry" ransomware.

ABC News' Amna Nawaz interviews chief investigative correspondent Brian Ross on the growing fears of a worldwide cyberattack.

Attack has affected more than 200,000 organization around the world.

A spokesperson from Europol said the attack appears to have been stabilized.

Ransomware spread throughout six continents before researchers discovered 'kill switch'.