Ransomware Rise: How the YES24 Cyberattack Reveals Global Digital Security Risks

Four days of total digital silence. That was the stark reality for the 20 million users of YES24, South Korea’s largest online bookstore, after a catastrophic ransomware attack forced the entire platform—website and app—offline. Orders for books, reservations for concerts, and access to digital resources vanished from reach. Recovery took five days, and the incident serves as a dramatic local case study of a global threat: ransomware, now one of the world’s fastest-growing and most devastating forms of cybercrime.

Ransomware: Anatomy of a Modern Cybercrime​

Ransomware—a portmanteau of “ransom” and “software”—encompasses any malware that infiltrates computer systems, encrypts their data, and demands a subsequent ransom, usually in cryptocurrency, to restore access. Gone are the days of hackers seeking merely to prove their technical prowess or to exfiltrate information for resale on dark web markets. Today’s ransomware operators are professionals, motivated by financial gain, often leveraging threats of public data leaks to increase pressure on victims who balk at paying up. If their demands aren’t met, confidential files—contracts, business information, customer records—may end up for sale on clandestine forums.
This exploitation model has gained both efficiency and impunity since the ascent of Bitcoin in 2009. Cryptocurrency makes it easy for attackers to evade traditional financial tracking, allowing criminals to operate across international borders with little fear of prosecution.

The YES24 Attack: A National Wake-Up Call​

The YES24 breach, which began on June 9th and lasted nearly a week, is singular in both its scale and its disruption. 20 million members were stripped of vital services; businesses that rely on YES24 for ticketing, logistics, and e-commerce saw their operations choked. That it took so long for the bookstore to even begin recovery, and that the attack came to public light only after a South Korean legislator exposed it, betrays the opacity with which many organizations respond to such incidents.
Analysis of the YES24 case revealed a preventable weakness. The company was running outdated operating systems—specifically, Windows Server 2012, for which Microsoft ended technical support late in 2023. Unpatched vulnerabilities made the platform a soft target. Once inside, attackers were free to encrypt data and position YES24 over a barrel until negotiations concluded.

Numbers that Shock: Ransomware’s Explosive Rise​

This isn’t an isolated event. According to a report by SK shieldus, over 2,575 ransomware incidents were recorded globally in the first quarter of this year—a jaw-dropping 122% year-over-year increase and a 35% uptick within a single quarter. In the last month alone, 484 known attacks were reported. Experts at security firm Cybersecurity Ventures anticipate global ransomware damages will soar from $57 billion in 2025 to a staggering $275 billion by 2031—nearly a fivefold increase.
South Korea, admired worldwide for its digital infrastructure, is feeling the squeeze. High-profile ransomware incidents this year have included not only YES24 but also a breach at the Ministry of Environment and an attack on Shinsung Deltatech, a prominent manufacturer. Notably, the manufacturing sector was hit by 114 attacks in a single month—about 24% of all known incidents in Korea—underscoring how vital data-driven industries are prime targets.

How Ransomware Works: Tools, Trends, and Tactics​

Multi-Stage Intrusions and Evolving Sophistication​

A contemporary ransomware campaign usually unfolds in phases:

• Initial Breach: Often via phishing emails, poisoned websites, or the exploitation of unpatched software (as was the case with YES24).
• Privilege Escalation: Attackers use advanced techniques—like exploiting the Windows Common Log File System (CLFS) zero-day vulnerability, or memory corruption flaws, granting them system-level rights.
• Credential Theft and Lateral Movement: With administrative access, they siphon user credentials and traverse the network, securing access to the most valuable data stores.
• Ransomware Activation: Data is encrypted, and a ransom note—sometimes via an onion domain, for anonymity—is delivered. Attackers may threaten to publish or sell confidential information.
• Double Extortion: Increasingly, groups exfiltrate data before encrypting it, adding leverage by threatening to leak or sell sensitive files if demands aren’t met.

In large-scale attacks, multiple advanced malware strains—like “PipeMagic,” used by seasoned ransomware collectives—are chained together, with kernel-level exploits granting nearly unlimited access.

The Role of Outdated Software​

Failure to upgrade or patch systems is a recurring theme. YES24’s use of Windows Server 2012 post-end-of-support exemplifies a broader industry malaise. Unpatched systems are honey traps for skilled adversaries, often targeted with well-known exploit kits or direct attacks on legacy vulnerabilities.
Similar cases are found globally. The infamous exploitation of the CLFS vulnerability (CVE-2025-29824) was linked to widespread Windows ransomware campaigns, some by the notorious RansomEXX/Storm-2460 group. Microsoft’s technical bulletins repeatedly emphasize prompt patching and migration to supported versions.

Ransomware-as-a-Service and the Rise of “Non-Expert” Cybercriminals​

The threat isn’t just the work of sophisticated in-house crews. “Ransomware-as-a-Service” (RaaS) now operates as a mature criminal business model. Platforms like RansomHub make sophisticated malware—and even revenue-sharing and tech support—available for a fee, dramatically widening access to powerful attack tools. Even technically unsophisticated criminals can launch effective ransomware campaigns simply by “renting” attack kits online. This widespread commercialization accelerates the creation of new ransomware groups and variants.

AI Tools and Phishing at Scale​

The latest twist: generative AI and large language models are starting to play significant roles in ransomware delivery. Malicious actors can generate convincingly tailored phishing emails, imitating organizations or insiders, at a scale and persuasion level never before seen. Consider the FunkSec group, which at the close of last year used LLMs for not just phishing, but for crafting ransomware code that evaded traditional security controls. This industrial-scale automation raises the barrier for defenders and lowers costs for attackers.

Disclosure Dilemmas: Why Companies Remain Silent​

In South Korea and elsewhere, there is evidence that many organizations opt to pay ransoms and quietly restore their systems without ever reporting the incident. National statistics likely understate the number of successful ransomware breaches, and attackers know it: the more invisible their campaign, the less likely they are to be prosecuted or blocked. The YES24 breach was only publicized after a government legislator named it ransomware rather than a “system outage.”
This culture of concealment is a double-edged sword for cybersecurity responders. On one hand, immediate restoration serves business interests. On the other, it encourages attackers, undermines incident statistics, and denies law enforcement the data needed for broader threat intelligence and effective public response.

Defensive Playbook: Prevention Over Cure​

When it comes to ransomware, after-the-fact “solutions” are elusive and unreliable—once files are encrypted, getting them back without a backup or the decryption keys is unrealistic. Prevention is paramount.
Core best practices include:

• Patch Management: Keep all systems, especially those running Microsoft Windows, fully updated. This applies equally to operating systems and application software.
• Backup Regimen: Maintain frequent, encrypted backups—offline, whenever possible. If backups are compromised or networked, they may also be encrypted during an attack.
• Employee Training: Regularly educate and test employees on recognizing phishing lures and suspicious attachments.
• Endpoint Detection and Response: Deploy real-time behavior monitoring and AI-driven EDR solutions to spot suspicious activities and stop attacks before they escalate.
• Network Configuration and Segmentation: Restrict access and monitor network segments. Lateral movement by attackers is often what turns a simple breach into a disaster.
• Principle of Least Privilege: Limit administrative accounts and baseline all network and user activity so deviations become quickly apparent in logs.
• Vendor and Supply Chain Assessment: Ensure third-party vendors also use modern, patched systems, and that remote access is tightly controlled.

In case of an attack, best practice globally is to disconnect affected systems immediately, perform a thorough forensic sweep, and consider reinstallation from trusted, clean sources. Authorities—including CISA and the FBI—strongly recommend against paying ransoms. There’s no guarantee of decryption, it perpetuates the crime, and may even attract future attacks.

Ransomware’s Economic Burden: Billions at Stake​

The cost of inaction is immense. Ransomware does not merely cause brief outages; it devastates business continuity, erodes customer trust, invites regulatory scrutiny, and transfers billions from legitimate commerce to criminal syndicates. South Korea’s bill is measured in the billions, and Cybersecurity Ventures estimates global losses will multiply fivefold in just the next several years.

Policy and Future Directions: From Compliance to Resilience​

The sheer scope and persistence of ransomware forces a reckoning for lawmakers, regulators, and business leaders alike. Critical infrastructure, including utilities and public services, is in the crosshairs—recent years have already seen attacks against everything from pipelines to judicial systems in the US, Brazil, and Europe.
Governments must strengthen incident disclosure requirements, broaden information sharing, and create incentives (or penalties) for prompt patching and transparent reporting. Organizations, in turn, should move beyond compliance checklists and foster a culture of cybersecurity—not just in IT, but across every staff level. That includes:

• Investing in AI-driven security solutions to battle AI-generated threats
• Re-evaluating vendor contracts with explicit patching and reporting requirements
• Building an incident response culture that is tested, documented, and shared

Critical Analysis: Strengths, Weaknesses, and Risks​

Strengths:

• The global cybersecurity community has responded rapidly to threats like CVE-2025-29824, releasing patches—and in some cases, unofficial workarounds—long before widespread exploitation. Modern EDR, backup, and data loss prevention solutions offer tangible defenses.
• Industry-wide information sharing and collaboration with authorities has improved, but is still not universal.

Risks and Weaknesses:

• Outdated and unpatched systems are everywhere—a fact starkly underlined by the YES24 breach. Many organizations, large and small, remain vulnerable due to budget or awareness gaps.
• Ransomware’s evolution, from cryptographic lockout to double extortion and RaaS, ensures amateurs can now operate at a professional level.
• Underreporting and silent ransom payments perpetuate the cycle and weaken collective response.
• The rapid adoption of generative AI makes phishing and attack customization vastly more scalable.

Verifiability Warning: While most statistics on attack volume and cost are corroborated by multiple independent security vendors and authorities, precise monetary damage estimates come with inherent uncertainty due to underreporting and differences in methodology. Similarly, claims about specific tactics, such as AI-generated phishing, reflect both documented cases and forecasts from informed experts, but their actual prevalence is difficult to quantify in real time.

Conclusion: Lessons from YES24 and the Road Ahead​

The ordeal faced by YES24 and its tens of millions of users could have been avoided—or at least curtailed—had basic security hygiene, especially timely operating system patching and backup discipline, been observed. This is not a uniquely Korean failure: organizations worldwide, across every sector, are in peril, and the consequences are only growing grimmer.
Ransomware is as much a business risk as it is a technical one. The question for every executive, IT administrator, and digital citizen is not “Will we be targeted?” but “Will we be resilient when it happens?”
The answer, according to incident after incident, is found not in secrecy, but in openness—swift disclosure, robust prevention, and continual adaptation. As the line between convenience and risk narrows and as attackers grow ever more sophisticated, only a culture of continuous vigilance and security-first thinking will keep us ahead of the next YES24.

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Source: Chosun Biz YES24 faces ransomware attack as global incidents rise, costing Korea billions