6 Worst US Data Breaches: From Ashley Madison to OPM Hack

Six major data breaches over the past decade have exposed the personal information of hundreds of millions of Americans, revealing critical vulnerabilities in both corporate and government security systems. From the Ashley Madison infidelity site hack to the massive Office of Personnel Management breach, these incidents demonstrate how stolen data can lead to financial ruin, personal tragedy, and national security threats.

Ashley Madison: When Infidelity Exposure Turned Deadly

The 2015 Ashley Madison breach exposed more than just data—it revealed secrets with potentially life-threatening consequences. Hackers calling themselves the Impact Team stole and released personal information of 37 million users from the infidelity website, including email addresses linked to U.S. military and government accounts. The attackers demanded the site’s parent company, Avid Life Media, shut down the service, warning that “adultery is punishable by death in Saudi Arabia.”

An analysis by Wired revealed that approximately 70% of the site’s users were male, and the breach reportedly led to at least two confirmed suicides. The exposure had devastating personal consequences as users faced blackmail, public humiliation, and relationship destruction. Avid Life Media ultimately faced a major class-action lawsuit and settled for millions, but the stolen data remains accessible online, continuing to haunt victims years later.

Vastaamo Therapy Center: Weaponizing Mental Health Records

In one of the most cruel breaches in history, Finnish mental health clinic Vastaamo saw its entire patient database stolen and used to blackmail vulnerable individuals. The attacker, later identified as Julius Kivimäki—a member of the infamous Lizard Squad hacking group—accessed unencrypted therapy notes and patient records, then demanded ransom payments directly from patients.

According to BBC reporting, the hacker systematically threatened to publish patients’ therapy session notes unless they paid thousands of euros. The breach demonstrated how cybercriminals could weaponize the most sensitive personal information, targeting people during their most vulnerable moments. Kivimäki’s motivation, as he later stated, was “mostly to raise awareness to ourselves,” highlighting the disturbing trend of hackers seeking notoriety through destructive attacks.

OPM Hack: China’s Massive Government Data Theft

The 2015 Office of Personnel Management breach represents one of the most significant national security failures in U.S. history, with Chinese hackers stealing security clearance files for 22.1 million federal employees and contractors. The breach included 18 million archived records, personnel files for 4.2 million individuals, and 5.6 million fingerprint images—creating a comprehensive intelligence goldmine.

Investigators traced the attack to a Chinese military hacking group after discovering they’d registered a third-party website under the name “Steve Rogers,” referencing Captain America. A CISA analysis noted that the OPM systems faced more than 10 million attempted intrusions monthly, but hackers exploited a specific vulnerability to gain unprecedented access. The stolen data included deeply personal information used in security clearance investigations, potentially compromising intelligence operations for years to come.

Equifax: Credit Bureau Failure Affects 147 Million

The 2017 Equifax breach exposed the personal and financial information of 147 million Americans, revealing catastrophic security failures at one of the nation’s three major credit reporting agencies. Hackers exploited a vulnerability in Apache Struts software that had a patch available since March—giving Equifax two months to secure its systems before the breach occurred in May.

According to the Government Accountability Office, Equifax failed to follow its own patching schedules, allowing attackers to steal names, Social Security numbers, birth dates, addresses, and driver’s license numbers. The company didn’t disclose the breach until September, leaving millions unaware their most sensitive financial data had been compromised. Equifax ultimately paid $700 million in settlements, including $300 million to affected customers, but the stolen information continues to circulate on dark web markets.

Democratic Committee Hacks: Election Interference Era

The 2016 hacking of Democratic National Committee and Clinton campaign emails marked a turning point in cyber warfare, demonstrating how data breaches could directly influence democratic processes. Russian hacking groups Fancy Bear and Cozy Bear accessed and leaked approximately 44,000 emails through DC Leaks and WikiLeaks, creating political chaos during a presidential election.

The Senate Intelligence Committee report confirmed that Russian operatives systematically weaponized the stolen information to sow discord and influence voter perceptions. The leaks spawned conspiracy theories like Pizzagate—which led to a armed man firing shots in a Washington pizza restaurant—and contributed to the rise of QAnon. The incident established a new paradigm where foreign actors could use stolen data as political weapons, undermining public trust in democratic institutions.

Salt Typhoon: China’s Telecom Infrastructure Invasion

Chinese hacking group Salt Typhoon conducted what security experts consider the worst telecommunications breach in U.S. history, infiltrating major carriers including AT&T, Verizon, and T-Mobile. The campaign, which security researchers believe is still ongoing, gave Chinese intelligence persistent access to American communications infrastructure.

According to Mandiant’s analysis, Salt Typhoon operators maintained long-term presence in telecom networks, enabling surveillance of communications and potential service disruption capabilities. The breach demonstrated how state-sponsored actors could compromise critical infrastructure, with security officials warning that completely removing such sophisticated hackers remains exceptionally difficult. The incident highlighted the vulnerability of essential services to nation-state cyber operations.