Week 20, 2024 security incident report

KakaoTalk Open Chat users' personal data leaked and traded illegally

65.8KImpact: Leak and posting of 696 people's data confirmed; at least 65,791 records estimated leaked

A hacker combined information obtained through a vulnerability in KakaoTalk Open Chat rooms and an illegal program using member serial numbers to identify individuals and sold the data. The Personal Information Protection Commission confirmed that the data of 696 people was leaked and posted and estimated at least 65,791 records were leaked. Kakao contested the imposition of the fine in court but lost in the first trial; the appeal then disputed whether personal data was leaked and whether protective measures were adequate.

Prosecutors appeal 4-year sentence for apartment wall pad hacker

A security expert was sentenced to four years in prison for hacking apartment wall pads across South Korea and spying on residents' homes. Prosecutors appealed the ruling.

Comedian Yoon Sung-ho's YouTube channel hacked

Impact: YouTube hacking and mental distress

Comedian Yoon Sung-ho, who performs as NewJeansNim, had his YouTube channel hacked. Yoon said on a broadcast in May 2024 that the hacking had caused him mental distress and that last year had been the hardest.

Ministry of Health and Welfare's X admin account hacked

Impact: Compromise of X administrator account

The administrator account of the Ministry of Health and Welfare on the social media platform X was hacked. The ministry said it reported the incident on May 16, 2024, and was working to recover the account.

Insider error at Cultural Heritage Administration leaks personal data of 2,000 people

2KImpact: Personal information of 2,000 people

Personal information of 2,000 people was leaked at South Korea's Cultural Heritage Administration due to an insider's mistake. Measures taken after the incident have not been confirmed.

Supreme Court rules victims must provide proof to receive compensation for personal data leaks

South Korea's Supreme Court ruled that victims must provide proof in order to receive compensation for a company's personal data leak. The company involved in the case, the scale of the leak and the date of the incident have not been confirmed.

MediSecure ransomware attack exposes data of 12.9 million

12.9MImpact: Personal information of 12.9 million Australians stolen

Australian e-prescription provider MediSecure suffered a large-scale ransomware attack and data breach, prompting an investigation by the Australian government. It was later confirmed that the personal information of 12.9 million Australians had been stolen. MediSecure said that, owing to its financial situation, it could not identify individual victims.

IRS contractor employee leaked data on 405,000 taxpayers

405KImpact: Tax return information of 405,000 taxpayers

An employee of an IRS contractor leaked taxpayers' tax return information. The scale of the damage confirmed in February 2025 was 405,000 taxpayers, about six times the previously reported figure. The IRS pursued improvements to information security, and Donald Trump filed a lawsuit in January 2026 seeking $10 billion over the leak.

Ashley Madison hack exposes data of millions of users

Impact: Information of millions of users leaked

In 2015, a hack of the affair-dating service Ashley Madison exposed the information of millions of users. Celebrities and clergy were among those on the leaked list, and the case of a pastor who took his own life after the leak also became known. The service continued operating after the incident.

Dubai property data leak reveals foreign figures' holdings

Impact: Disclosure of Dubai property ownership records

Leaked Dubai real estate data revealed the property holdings of politicians, former military personnel and others from various countries. The data also included information on luxury homes linked to people involved in the OneCoin cryptocurrency fraud. Pakistani politicians said they had lawfully declared the assets, while the United Arab Emirates dismissed the claims of Dubai Unlocked.

Nissan North America ransomware attack exposes data of over 53,000 employees

53KImpact: Personal information including Social Security numbers of more than 53,000 current and former employees

Nissan North America was attacked in November 2023, exposing the personal information of more than 53,000 current and former employees. The leaked information included Social Security numbers, and the attackers targeted an external VPN before shutting down some systems and demanding money. In March 2026, a $1.5 million settlement was reached over the incident.