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SK Telecom Malware Attack Exposes USIM Data in South Korea

 

SK Telecom, South Korea’s top mobile carrier, has disclosed a security incident involving a malware infection that exposed sensitive information tied to users’ Universal Subscriber Identity Modules (USIMs). The breach was detected on the night of April 19, 2025, during the weekend when many companies operate with reduced cybersecurity staffing. 

With nearly half of South Korea’s mobile market share and around 34 million subscribers, SK Telecom holds a crucial position in the country’s telecommunications sector. In an official statement, the company explained that malware had infiltrated parts of its network, prompting immediate action to contain the threat. 

The affected systems were isolated swiftly, and the malicious software was removed. So far, SK Telecom has stated there is no confirmed misuse of customer data linked to this breach. This was reported to the Korea Internet & Security Agency (KISA) on April 20, and to the Personal Information Protection Commission. 
Investigations are ongoing to determine how the attackers gained access and the extent of the data exposed. USIM cards store essential data such as International Mobile Subscriber Identity (IMSI) numbers, phone numbers (MSISDN), encryption keys for network authentication, and sometimes even stored contacts or text messages. Unauthorized access to this information could enable cybercriminals to conduct targeted surveillance, track users’ locations, or perform SIM-swapping attacks that could compromise online accounts and digital assets. 

In response, SK Telecom has strengthened security around USIM card management, increasing checks on SIM card replacement activities and monitoring authentication processes for suspicious behavior. Accounts showing irregular activities could face automatic suspension to prevent potential fraud. Additionally, the carrier is advising customers to activate their USIM protection service, a preventive measure that restricts unauthorized SIM swaps, adding extra protection to user accounts. 

A hacking group is yet to claim responsibility for the breach. SK Telecom emphasized that while the malware was neutralized quickly, they remain vigilant and are working closely with cybersecurity authorities to uncover more details about the intrusion and enhance future protections. 

This breach highlights ongoing risks faced by large mobile operators, especially during periods when cyber defenses might be less robust. It also underscores the critical need for mobile carriers to adopt continuous security monitoring and proactive measures to protect customer data from emerging threats. 

As investigations continue, SK Telecom has committed to updating customers and regulators about any new findings or developments related to the incident.

Windows CLFS Zero-Day CVE-2025-29824 Exploited by Ransomware Group Storm-2460

 

A newly disclosed Windows zero-day vulnerability, tracked as CVE-2025-29824, is being actively exploited in cyberattacks to deliver ransomware, Microsoft has warned. This flaw affects the Windows Common Log File System (CLFS) driver and enables local privilege escalation—a method often used by attackers after gaining initial access. 

Microsoft’s Threat Intelligence and Security Response teams revealed that the bug is classified as a “use-after-free” vulnerability with a severity score of 7.8. While attackers need to compromise a system before they can exploit this flaw, it remains highly valuable in ransomware operations. Cybercriminals often rely on these types of vulnerabilities to turn a limited foothold into full administrative control across networks. 

The cybercrime group currently leveraging this zero-day is known as Storm-2460. Microsoft reports that the group is using the exploit to deploy a custom backdoor named PipeMagic, which in turn facilitates the installation of RansomEXX ransomware—a variant not commonly observed but still capable of serious disruption. So far, Storm-2460 has targeted organizations in industries such as IT, finance, and retail, with victims located in countries including the United States, Spain, Saudi Arabia, and Venezuela. 

Microsoft emphasized that the number of known cases remains small, but the sophistication of the exploit is concerning. This attack is notable for being part of a “post-compromise” campaign, meaning the attacker already has a presence within the system before using the flaw. These types of exploits are frequently used to escalate privileges and move laterally within a network, eventually leading to broader ransomware deployment. Microsoft issued a security advisory for CVE-2025-29824 on April 8 and urged organizations to install updates immediately. Failure to do so could leave critical systems vulnerable to privilege escalation and full network compromise. 

To mitigate risk, Microsoft advises businesses to prioritize patch management, restrict unnecessary administrative privileges, and closely monitor for unusual behavior across endpoints. Cybersecurity teams are also encouraged to review logs for any indicators of compromise related to PipeMagic or RansomEXX. As ransomware tactics continue to evolve, the exploitation of vulnerabilities like CVE-2025-29824 reinforces the need for proactive defense strategies and rapid incident response protocols.

WhatsApp Windows Vulnerability CVE-2025-30401 Could Let Hackers Deliver Malware via Fake Images

 

Meta has issued a high-priority warning about a critical vulnerability in the Windows version of WhatsApp, tracked as CVE-2025-30401, which could be exploited to deliver malware under the guise of image files. This flaw affects WhatsApp versions prior to 2.2450.6 and could expose users to phishing, ransomware, or remote code execution attacks. The issue lies in how WhatsApp handles file attachments on Windows. 

The platform displays files based on their MIME type but opens them according to the true file extension. This inconsistency creates a dangerous opportunity for hackers: they can disguise executable files as harmless-looking images like .jpeg files. When a user manually opens the file within WhatsApp, they could unknowingly launch a .exe file containing malicious code. Meta’s disclosure arrives just as new data from online bank Revolut reveals that WhatsApp was the source of one in five online scams in the UK during 2024, with scam attempts growing by 67% between June and December. 

Cybersecurity experts warn that WhatsApp’s broad reach and user familiarity make it a prime target for exploitation. Adam Pilton, senior cybersecurity consultant at CyberSmart, cautioned that this vulnerability is especially dangerous in group chats. “If a cybercriminal shares the malicious file in a trusted group or through a mutual contact, anyone in that group might unknowingly execute malware just by opening what looks like a regular image,” he explained. 

Martin Kraemer, a security awareness advocate at KnowBe4, highlighted the platform’s deep integration into daily routines—from casual chats to job applications. “WhatsApp’s widespread use means users have developed a level of trust and automation that attackers exploit. This vulnerability must not be underestimated,” Kraemer said. Until users update to the latest version, experts urge WhatsApp users to treat the app like email—avoid opening unexpected attachments, especially from unknown senders or new contacts. 

The good news is that Meta has already issued a fix, and updating the app resolves the vulnerability. Pilton emphasized the importance of patch management, noting, “Cybercriminals will always seek to exploit software flaws, and providers will keep issuing patches. Keeping your software updated is the simplest and most effective protection.” For now, users should update WhatsApp for Windows immediately to mitigate the risk posed by CVE-2025-30401 and remain cautious with all incoming files.

Ransomware Found in VSCode Extensions Raises Concerns Over Microsoft’s Security Review

 

Cybersecurity experts have discovered ransomware hidden within two Visual Studio Code (VSCode) Marketplace extensions, raising concerns about Microsoft’s ability to detect malicious software in its platform. The compromised extensions, named “ahban.shiba” and “ahban.cychelloworld,” were downloaded by users before security researchers flagged them and they were subsequently removed. 

Despite Microsoft’s security measures, the extensions remained publicly accessible for a significant period, highlighting potential gaps in the company’s review process. The “ahban.cychelloworld” extension was first uploaded on October 27, 2024, followed by “ahban.shiba” on February 17, 2025. The VSCode Marketplace, designed to provide developers with additional tools for Microsoft’s popular coding platform, has come under scrutiny for failing to identify these threats. 

Researchers at ReversingLabs determined that both extensions included a PowerShell script that connected to a remote Amazon Web Services (AWS) server to download further malicious code. This secondary payload functioned as ransomware, though evidence suggests it was still in a testing phase. 

Unlike traditional ransomware that encrypts entire systems, this malware specifically targeted files stored in C:\users%username%\Desktop\testShiba.  Once the encryption was complete, victims received a Windows notification stating: “Your files have been encrypted. Pay 1 ShibaCoin to ShibaWallet to recover them.” However, no further instructions or payment details were provided, suggesting the malware was not yet fully developed.  

Although Microsoft eventually removed the extensions, security researcher Italy Kruk from ExtensionTotal disclosed that their automated detection system had identified the malicious code much earlier. Kruk stated that they had alerted Microsoft about the issue but received no response. Further analysis revealed that the initial version of “ahban.cychelloworld” was clean, but the ransomware was introduced in version 0.0.2, which was released on November 24, 2024. ExtensionTotal flagged this version to Microsoft on November 25, yet the extension remained available for months. 

During this time, five more versions were uploaded, all containing the same ransomware. This case has intensified concerns about Microsoft’s ability to monitor third-party extensions effectively. The security lapse within the VSCode Marketplace highlights the risk developers face when downloading extensions, even from official sources. Microsoft has previously faced criticism for both slow responses to security threats and for mistakenly removing non-malicious extensions. 

A notable example involved two popular VSCode themes, ‘Material Theme – Free’ and ‘Material Theme Icons – Free,’ which were taken down due to suspected obfuscated JavaScript. However, after further review, Microsoft determined the extensions were safe, reinstated them, and apologized, promising improvements to its security screening process. The presence of ransomware in widely used developer tools underscores the need for stronger security measures. Developers must stay cautious, regularly update security protocols, and carefully evaluate third-party extensions before installing them, even when they come from official platforms like the VSCode Marketplace.

Arcane Malware Steals VPN, Gaming, and Messaging Credentials in New Cyber Threat

 

A newly identified malware strain, Arcane, is making headlines for its ability to steal a vast range of user data. This malicious software infiltrates systems to extract sensitive credentials from VPN services, gaming platforms, messaging apps, and web browsers. Since its emergence in late 2024, Arcane has undergone several modifications, increasing its effectiveness and expanding its reach. 

Unlike other cyber threats with long-established histories, Arcane is not linked to previous malware versions carrying a similar name. Analysts at Kaspersky have observed that the malware primarily affects users in Russia, Belarus, and Kazakhstan. This is an unusual pattern, as many Russian-based cybercriminal groups tend to avoid targeting their home region to steer clear of legal consequences. 

Additionally, communications linked to Arcane’s operators suggest that they are Russian-speaking, reinforcing its likely origin. The malware spreads through deceptive content on YouTube, where cybercriminals post videos promoting game cheats and cracked software. Viewers are enticed into downloading files that appear legitimate but contain hidden malware. Once opened, these files initiate a process that installs Arcane while simultaneously bypassing Windows security settings. 

This allows the malware to operate undetected, giving hackers access to private information. Prior to Arcane, the same group used a different infostealer known as VGS, a modified version of an older trojan. However, since November 2024, they have shifted to distributing Arcane, incorporating a new tool called ArcanaLoader. This fake installer claims to provide free access to premium game software but instead delivers the malware. 

It has been heavily marketed on YouTube and Discord, with its creators even offering financial incentives to content creators for promoting it. Arcane stands out because of its ability to extract detailed system data and compromise various applications. It collects hardware specifications, scans installed software, and retrieves login credentials from VPN clients, communication platforms, email services, gaming accounts, and cryptocurrency wallets. Additionally, the malware captures screenshots, which can expose confidential information visible on the victim’s screen. 

Though Arcane is currently targeting specific regions, its rapid evolution suggests it could soon expand to a broader audience. Cybersecurity experts warn that malware of this nature can lead to financial theft, identity fraud, and further cyberattacks. Once infected, victims must reset all passwords, secure compromised accounts, and ensure their systems are thoroughly cleaned. 

To reduce the risk of infection, users are advised to be cautious when downloading third-party software, especially from unverified sources. Game cheats and pirated programs often serve as delivery methods for malicious software, making them a significant security threat. Avoiding these downloads altogether is the safest approach to protecting personal information.

The Growing Threat of Infostealer Malware: What You Need to Know

 

Infostealer malware is becoming one of the most alarming cybersecurity threats, silently stealing sensitive data from individuals and organizations. This type of malware operates stealthily, often going undetected for long periods while extracting valuable information such as login credentials, financial details, and personal data. As cybercriminals refine their tactics, infostealer attacks have become more frequent and sophisticated, making it crucial for users to stay informed and take preventive measures. 

A significant reason for concern is the sheer scale of data theft caused by infostealers. In 2024 alone, security firm KELA reported that infostealer malware was responsible for leaking 3.9 billion passwords and infecting over 4.3 million devices worldwide. Similarly, Huntress’ 2025 Cyber Threat Report revealed that these threats accounted for 25% of all cyberattacks in the previous year. This data highlights the growing reliance of cybercriminals on infostealers as an effective method of gathering personal and corporate information for financial gain. 

Infostealers operate by quietly collecting various forms of sensitive data. This includes login credentials, browser cookies, email conversations, banking details, and even clipboard content. Some variants incorporate keylogging capabilities to capture every keystroke a victim types, while others take screenshots or exfiltrate files. Cybercriminals often use the stolen data for identity theft, unauthorized financial transactions, and large-scale corporate breaches. Because these attacks do not immediately disrupt a victim’s system, they are harder to detect, allowing attackers to extract vast amounts of information over time. Hackers distribute infostealer malware through multiple channels, making it a widespread threat. 

Phishing emails remain one of the most common methods, tricking victims into downloading infected attachments or clicking malicious links. However, attackers also embed infostealers in pirated software, fake browser extensions, and even legitimate platforms. For example, in February 2025, a game called PirateFi was uploaded to Steam and later found to contain infostealer malware, compromising hundreds of devices before it was removed. Social media platforms, such as YouTube and LinkedIn, are also being exploited to spread malicious files disguised as helpful tools or software updates. 

Beyond stealing data, infostealers serve as an entry point for larger cyberattacks. Hackers often use stolen credentials to gain unauthorized access to corporate networks, paving the way for ransomware attacks, espionage, and large-scale financial fraud. Once inside a system, attackers can escalate their access, install additional malware, and compromise more critical assets. This makes infostealer infections not just an individual threat but a major risk to businesses and entire industries.  

The prevalence of infostealer malware is expected to grow, with attackers leveraging AI to improve phishing campaigns and developing more advanced evasion techniques. According to Check Point’s 2025 Cybersecurity Report, infostealer infections surged by 58% globally, with Europe, the Middle East, and Africa experiencing some of the highest increases. The SYS01 InfoStealer campaign, for instance, impacted millions across multiple continents, showing how widespread the issue has become. 

To mitigate the risks of infostealer malware, individuals and organizations must adopt strong security practices. This includes using reliable antivirus software, enabling multi-factor authentication (MFA), and avoiding downloads from untrusted sources. Regularly updating software and monitoring network activity can also help detect and prevent infections. Given the growing threat, cybersecurity awareness and proactive defense strategies are more important than ever.

Medusa Ransomware Attacks: CISA, FBI, and MS-ISAC Issue #StopRansomware Advisory

 

The Cybersecurity and Infrastructure Security Agency (CISA), in partnership with the FBI and the Multi-State Information Sharing and Analysis Center (MS-ISAC), has issued a #StopRansomware advisory, warning organizations about the increasing threat of Medusa ransomware. 

Medusa, a ransomware-as-a-service (RaaS) variant, was first detected in 2021 and has since targeted over 300 victims across multiple critical infrastructure sectors. Industries such as healthcare, law, education, insurance, technology, and manufacturing have been particularly affected, highlighting the wide reach and severity of the ransomware’s impact. Medusa initially operated as a closed ransomware variant, meaning its developers had full control over its deployment and operations. 

Over time, it transitioned to an affiliate-based model, allowing external cybercriminals to use the ransomware while keeping certain aspects, such as ransom negotiations, under the control of the original developers. This shift has allowed Medusa to expand its reach, increasing its effectiveness as a cyber threat. Medusa demands ransoms ranging from $100,000 to as much as $15 million. 

Like many modern ransomware variants, it employs double extortion tactics—stealing sensitive data before encrypting victim networks. This strategy puts additional pressure on victims, as attackers can threaten to leak or sell stolen data if the ransom is not paid. Cybersecurity researchers from Symantec’s Threat Hunter team recently reported a rise in Medusa-related attacks over the past year. 

Medusa’s developers use initial access brokers (IABs) to gain entry into victim networks. These brokers operate within cybercriminal forums and marketplaces, selling access to compromised systems for amounts ranging from $100 to $1 million. Medusa affiliates rely on phishing campaigns and vulnerability exploitation to gain initial access, making it crucial for organizations to bolster their email security and patch known vulnerabilities. Once inside a system, Medusa operators use “living-off-the-land” (LotL) techniques, leveraging legitimate system tools to evade detection while conducting reconnaissance, data theft, and lateral movement.

Given Medusa’s evolving tactics, cybersecurity experts stress the importance of proactive defense measures. Organizations should deploy security patches, implement network segmentation, and restrict access to critical services from untrusted sources. Dan Lattimer, area vice president for Semperis in the UK and Ireland, emphasized the need for an “assumed breach” mindset, urging companies to shift from a prevention-focused approach to rapid detection, response, and recovery. 

As ransomware attacks grow more sophisticated, organizations must remain vigilant, continuously updating their cybersecurity strategies to mitigate risks and strengthen their defenses against threats like Medusa.

New Malware Impersonates Browser Extensions to Steal Login Credentials

 

Cybercriminals are continually evolving their tactics to evade antivirus detection and trick users into installing malicious software. One of the latest threats involves malware that impersonates legitimate browser extensions, allowing attackers to steal login credentials while remaining undetected. Although this discovery is concerning, researchers have identified the vulnerability before it could be widely exploited, giving security teams time to respond. 

According to a report by SquareX Labs, this attack starts with scammers developing seemingly useful browser extensions, such as an AI-powered transcription tool. To avoid malware detection, they distribute the extension outside official platforms like the Chrome Web Store or Google Play. Users are then encouraged to pin the extension for easy access, allowing it to quietly monitor their browsing habits over time. 

Once installed, the malicious extension collects data on the user’s existing extensions, particularly those used for handling sensitive information, such as password managers. When the right opportunity arises, it disables the legitimate extension and replaces its icon with an identical version. If the user attempts to access their password manager, they unknowingly interact with the fake extension instead. 

To further deceive users, the fraudulent extension displays a message stating that their session has expired, requiring them to log in again. However, rather than accessing their accounts, victims unknowingly submit their credentials directly to cybercriminals. With this information, attackers can break into password vaults, gaining access to sensitive data, stored passwords, and linked accounts. This method is particularly dangerous because it exploits trust in well-known extensions. 

Unlike traditional phishing attempts, which rely on fake websites or deceptive emails, this attack leverages the user’s own browser environment, making it harder to detect. Victims may not realize they’ve been compromised until they notice unauthorized activity on their accounts. Despite the sophistication of this attack, there is no immediate reason for panic. Security researchers identified the exploit before cybercriminals could widely deploy it, and browser developers have been alerted to the risk. 

However, this incident underscores the importance of practicing good cybersecurity habits. Users should only install browser extensions from trusted sources like the Chrome Web Store, avoid third-party downloads, and check reviews before installation. 

Additionally, enabling multi-factor authentication (MFA) on important accounts can provide an extra layer of security, reducing the risk of credential theft. As cyber threats continue to evolve, staying informed and cautious about software installations remains crucial to maintaining online security.