Lessons from the Largest Cyber Attacks of 2025

Cyber Attacks of 2025 Introduction

As the year approaches its midpoint, the world has witnessed a surge in large-scale cyber attacks in 2025 that have disrupted entire industries. Retailers, financial institutions, and even government agencies have faced challenges ranging from temporary shutdowns to massive data leaks. The frequency and severity of these incidents underscore the complex digital relationships that underpin modern commerce and governance, highlighting the need to prepare for a threat landscape that grows increasingly sophisticated by the day. Companies that fail to adapt quickly risk exposing critical information, losing revenue, and damaging their reputation. This blog post serves as a reminder of the biggest Cyber attacks of 2025, and I will provide some lessons learned.  

Background: The Evolving Threat Landscape

Technology has generated interconnected networks that bring remarkable efficiencies but also create new vulnerabilities. A single weak link in a supply chain can prompt widespread operational failures. Attackers are exploiting these connections and the fact that third-party providers manage numerous systems. Furthermore, criminal groups employ a range of tactics, from zero-day exploits to social engineering, to gain unauthorized access to privileged systems. This shift means that businesses cannot rely solely on perimeter defenses; robust internal controls, vigilant monitoring, and consistent collaboration with partners are increasingly critical. Regulatory agencies are also paying closer attention to how data is secured, making compliance an ongoing challenge for enterprises with global footprints.

Cyber Attacks of 2025

The UNFI Cyberattack — Disruption in the Food Supply Chain

One of the most unsettling attacks this year targeted a major food distributor, United Natural Foods Inc. (UNFI). In June, a malicious intrusion led to the shutdown of electronic ordering and delivery services, disrupting essential grocery supply lines throughout North America. As retailers scrambled to find alternative sources of goods, supermarkets contended with inventory shortages and logistical hurdles. The incident highlighted the grocery industry’s reliance on seamless digital infrastructure and how quickly a disruption can spread across an entire sector.

Sepah Bank — 42 Million Records Compromised

Financial institutions have long been a target for cybercriminals, and in March, Iran’s Bank Sepah became a high-profile example. A hacking group managed to access approximately 42 million customer records, including confidential data about senior officials. The attackers made a steep cryptocurrency ransom demand and even released portions of the stolen data when their terms were not met. This breach highlighted that banking networks, particularly those that are not sufficiently segmented or encrypted, can be highly vulnerable targets for groups seeking to profit from selling or exploiting sensitive personal and financial information.

TeleMessage Breach — U.S. Officials Exposed

Another notable incident occurred in May when cybercriminals compromised TeleMessage, a messaging service used by several U.S. government agencies. Although content from the conversations was not leaked, important metadata, including names and contact details, was revealed. This event immediately raised alarms about the dangers of even seemingly minor data exposures. When critical entities such as federal departments are implicated, the potential for national security concerns and counterintelligence exploitation becomes very real. Close evaluation of third-party app security is essential in preventing similar breaches.

SAP NetWeaver Vulnerability — Cloud Infrastructure at Risk

In April, a critical zero-day flaw in SAP NetWeaver Visual Composer (CVE-2025-31324) was discovered. Attackers who exploited this vulnerability could upload malicious files, gaining remote code execution privileges. Over 500 NetWeaver instances were identified as actively compromised worldwide, highlighting the rapid exploitation of newly discovered weaknesses by cybercriminals. Many of these systems power the most vital functions of an enterprise, from resource planning to financial accounting, so public and private sector organisations alike were pressured to implement patches and step up security monitoring.

M&S Cyberattack — UK Retail Operations Affected

Over the Easter holiday, a persistent threat group successfully exploited weaknesses in a contractor’s defenses, crippling the online platforms of Marks & Spencer (M&S) for nearly six weeks. Click-and-collect, fashion sales, and other digital services were inoperable. Beyond the immediate impact on revenue, the prolonged disruption tarnished consumer trust during a crucial retail season. This attack highlighted the devastating effect of a successful breach, particularly when it occurs during periods of high customer activity.

Lessons Learned From the Cyber Attacks of 2025

These incidents, with their staggering financial and operational consequences, point to a set of universal lessons. First, complex supply chains are fragile; a single outage or system failure at a key distributor can create ripple effects across an industry. Second, data oversight and protection remain critical. Attackers continue to target private information for blackmail, ransom, or resale. Third, businesses must be prepared for sophisticated exploits that may bypass traditional defences and exploit small lapses in layered security. Finally, vendor oversight is a priority: many successful breaches begin with third-party providers that operate under weaker security protocols, providing attackers a backdoor into core systems.

Recommended Best Practices & Strategies

Moving forward, businesses can significantly reduce cyber risks by paying careful attention to their environments as well as those of their partners. Creating a robust incident response plan, supported by frequent drills, helps ensure that teams know exactly how to contain and recover from attacks. Ongoing training fosters a security-conscious culture where employee errors, such as responding to phishing messages, are less likely to occur. Furthermore, systematic patch management and vulnerability scanning enable companies to address weaknesses before criminals can exploit them. Implementing zero-trust architecture is also gaining relevance, requiring continuous verification for every user or process, regardless of their affiliation or historical reliability.

“Timely threat intelligence and rigorous internal controls aren’t optional extras—they are the cornerstones of cyber resilience in a hyperconnected world,” says John Pohlman. “Cybercriminals are relentless, but disciplined security measures can often outpace their attacks.”

How Tanner Can Help

Tanner’s cybersecurity team provides a comprehensive approach to digital risk management. We help clients identify vulnerabilities through thorough risk assessments and penetration tests, and assist in designing secure IT infrastructures that are both modern and resilient. Our specialists are proficient in incident response planning, ensuring that every client has a roadmap for swift containment and recovery in the event of a breach. We also offer guidance on regulatory compliance, helping businesses meet evolving requirements and demonstrate readiness to auditors, boards, and customers.

From onboarding new third-party providers to refining data protection policies, our experts are prepared to support organizations in building a security posture that can withstand the evolving threats of 2025 and beyond.

Cyber Attacks of 2025 Conclusion

The most significant cyberattacks of this year serve as a reminder that every sector, from financial services to consumer retail, is vulnerable. Embracing continuous monitoring, implementing swift incident response strategies, and collaborating actively with security experts can help organisations stay one step ahead of potential attackers. By learning from the lessons of these incidents and partnering with trusted advisors, businesses can enhance their long-term resilience. It is never too early or too late to test and strengthen your IT controls to protect against the next wave of cyber threats.