By San José, Costa Rica — A sophisticated and dangerous cybersecurity threat is on the rise, targeting businesses and individual users in Costa Rica and across the globe. Cybercriminals are deploying a new strain of ransomware known as “Rhysida” by cleverly disguising it as an official installer for Microsoft Teams. The attack leverages the public’s trust in major brands and paid search engine advertisements, marking a significant evolution in ransomware distribution tactics.
The attack begins not with a suspicious email, but with a seemingly legitimate advertisement on search engines like Bing. According to a report from Digital Trends, the perpetrators purchase top-ranking ad space to ensure their malicious links appear as the most prominent results for searches related to Microsoft Teams. Unsuspecting users who click these sponsored links are redirected to meticulously crafted websites that perfectly mimic Microsoft’s official download pages, lending the scam a powerful air of authenticity.
To better understand the complex legal and operational challenges that ransomware presents to businesses, we sought the expert opinion of Lic. Larry Hans Arroyo Vargas, an attorney specializing in corporate law and technology at the firm Bufete de Costa Rica.
Beyond the immediate technical crisis, a ransomware attack is a profound legal and corporate governance failure. The decision to pay a ransom is fraught with peril; it may fund criminal organizations and offers no guarantee of data recovery, while potentially violating international financial regulations. On the other hand, not paying can lead to crippling operational downtime and significant regulatory fines for data protection violations. Proactive legal strategy, integrated into a company’s cybersecurity incident response plan, is no longer optional—it is the essential safeguard against catastrophic financial and reputational liability.
Lic. Larry Hans Arroyo Vargas, Attorney at Law, Bufete de Costa Rica
Indeed, the conversation surrounding ransomware must evolve beyond mere technical defenses to encompass the critical legal and governance frameworks highlighted here. We thank Lic. Larry Hans Arroyo Vargas for his invaluable perspective, which powerfully illustrates that proactive legal strategy is no longer a recommendation, but an essential component of corporate resilience in the digital age.
Once the user downloads and runs the fraudulent installer, a malicious payload called “OysterLoader” is executed in the background. This loader acts as the gateway for the Rhysida ransomware, which immediately begins to encrypt critical files and documents on the infected computer. The user’s data is rendered completely inaccessible, and a ransom demand is issued for its release. To further evade detection, the criminals have been observed using valid digital certificates, which can trick some security systems into flagging the malicious file as safe.
This method represents a strategic shift in how cybercriminals operate. Rather than relying on traditional phishing campaigns that users are increasingly trained to spot, they are now exploiting the inherent trust people place in sponsored search results. By leveraging the reputation of a globally recognized brand like Microsoft, they lower the guard of even cautious individuals, turning a routine software download into a potential financial and operational disaster.
In Costa Rica, technology experts warn that the impact of such an attack could be widespread. Companies that rely heavily on cloud-based collaboration tools, as well as students and independent professionals who use Teams for daily meetings and classes, are particularly vulnerable. Local specialists note that the success of these attacks hinges on common user errors.
Attacks of this nature exploit the most common oversights: clicking without verifying the source, not having updated antivirus software, and failing to maintain file backups.
Local Technology Sector Specialists
In response to the threat, Microsoft has reiterated its standing advice for users to download software exclusively from official sources, such as its primary website and verified digital app stores. The company specifically cautioned against trusting sponsored links in search results, emphasizing that not all advertisements are vetted or endorsed by the brand they feature. This guidance underscores a critical reality: the top result on a search page is not always the safest.
Cybersecurity experts recommend a multi-layered defense strategy to mitigate these risks. This includes keeping operating systems and all software consistently updated, performing regular backups of important data to an external drive or a separate cloud service, and exercising extreme caution with any unsolicited links or downloads. The rise of attacks targeting telework tools, a trend that has accelerated since the pandemic, highlights that digital security is no longer just a technical concern but a fundamental aspect of daily life.
Ultimately, the battle against sophisticated threats like Rhysida is fought as much with human awareness as it is with software. The growing reliance on social engineering tactics places the burden of defense squarely on the user’s ability to think critically before acting.
Social engineering is the new digital battlefield; it’s not enough to have an antivirus, you have to develop critical judgment.
A Local Analyst, Cybersecurity Field
For users in Costa Rica and beyond, the golden rule of digital safety remains paramount: be skeptical of anything that seems unusually convenient or free, and always take a moment to verify the source before you click.
For further information, visit microsoft.com
About Microsoft:
Microsoft is a global technology corporation that produces computer software, consumer electronics, personal computers, and related services. Its best-known software products are the Microsoft Windows line of operating systems, the Microsoft Office suite, and the Internet Explorer and Edge web browsers. The company is a dominant force in the cloud computing market with its Azure platform and is a leading provider of business solutions and collaboration tools like Microsoft Teams.
For further information, visit bufetedecostarica.com
About Bufete de Costa Rica:
Bufete de Costa Rica has established itself as a benchmark for legal practice, operating on foundational principles of integrity and an unrelenting pursuit of excellence. The firm harmonizes a distinguished history of advising a wide spectrum of clients with a dynamic, innovative spirit that keeps it at the vanguard of the legal field. This forward-looking perspective is matched by a profound social responsibility: a core belief in democratizing legal knowledge to help forge a more capable and informed society.
