network detection Archives

Tech Optimizer

February 16, 2026

Researchers Uncover OysterLoader, an Advanced Obfuscated Loader Powering Rhysida Attacks

OysterLoader, a sophisticated malware loader also known as Broomstick and CleanUp, has emerged as a significant threat since mid-2024. It is a multi-stage downloader linked to ransomware attacks and data theft, particularly associated with the Rhysida ransomware group. Written in C++, it infiltrates systems through malicious websites that impersonate legitimate software download platforms, tricking victims into executing a signed Microsoft Installer (MSI) that launches the malware. OysterLoader employs a four-stage infection chain designed to evade detection. The first stage uses a packer named TextShell to load hidden code into memory, creating an illusion of legitimacy through harmless Windows API calls. The second stage decompresses a concealed payload using a modified LZMA algorithm. The third stage functions as a downloader and environment tester, establishing contact with its command-and-control (C2) server via HTTPS. In the final stage, OysterLoader installs a malicious DLL that executes every 13 minutes through the Windows Task Scheduler, communicating with multiple hardcoded servers and transmitting critical system information. The malware uses customized Base64 encoding and variable communication endpoints to evade detection. Its primary objective is to ensure persistence and facilitate the delivery of additional payloads, including ransomware and credential stealers. Security analysts predict that OysterLoader will remain a formidable threat through 2026, particularly for organizations downloading administrative tools from unverified sources. Indicators of Compromise (IOC): - Mutex: h6p#dx!&fse?%AS! - Task: COPYING3 (rundll32 DllRegisterServer) - C2 Domain: grandideapay[.]com/api/v2/facade - RC4 Key: vpjNm4FDCr82AtUfhe39EG5JLwuZszKPyTcXWVMHYnRgBkSQqxzBfb6m75HZV3UyRY8vPxDna4WC2KMAgJjQqukrFdELXeGNSws9SBFXnYJ6ExMyu97KCebD5mTwaUj42NPAvHdkGhVtczWgfrZ3sLyRZg4HuX97AnQtK8xvpLU2CWDhVq5PEfjTNz36wdFasecBrkGSDApf83d6NMyaJCsvcRBq9ZYKthjuw5S27EVzWrPHgkmUxFL4bQSgMa4F - IP: 85.239.53.66

Tech Optimizer

November 5, 2025

Hackers Are Using Linux Malware to Invisibly Bypass Windows Security

Hackers are refining tactics to evade detection by EDR systems and antivirus software, with a notable strategy being the use of Linux malware to infiltrate Windows systems. Investigations by Bitdefender and CERT-GE revealed a campaign by the Russian hacker group Curly COMrades, which exploits the Hyper-V virtualization platform on Windows 10 to create covert access channels. They utilize Alpine Linux for lightweight virtual machines that are difficult to detect, requiring only 120 MB of disk space and 256 MB of RAM. The attackers maintain persistent access using tools like Resocks and Stunnel, starting their activities in early July 2024 by activating Hyper-V on compromised systems and deploying misleading virtual machines labeled “WSL.” They introduced custom malware, CurlyShell and CurlCat, for communication and remote access. This trend of using Linux malware against Windows systems is growing, as seen in recent Qilin ransomware attacks documented by Trend Micro.

Winsage

February 21, 2025

Windows 11 24H2 RDP hangs on login, RDP session connecting issues reported

Windows 11 has a significant issue affecting Remote Desktop Protocol (RDP) sessions during the login phase, potentially linked to the Windows 11 24H2 update or recent security updates KB5050094 and KB5051987. Administrators have reported difficulties in establishing RDP connections since the rollout of the 24H2 update, with issues persisting even when the RDP service is operational and firewall configurations are correct. Users have noted that changing the default RDP port from 3389 may resolve connection issues for some, although this workaround is not universally effective. Additionally, there are reports of RDP sessions hanging during the login process, particularly when reconnecting to previously disconnected sessions. To address the hanging issue, users can modify settings in the Group Policy Editor by enabling the "Select network detection on the server" policy and turning off Connect Time Detect and Continuous Network Detect. A system reboot is not necessary, but executing the gpupdate /force command is recommended. Alternatively, a Windows Registry script can be used to automate the process across multiple devices. As of February 21, Microsoft has not officially acknowledged these network issues, despite their widespread impact on users.