InfoSecBulletin Cybersecurity for mankind
Sygnia’s recent report highlights the changing strategies of ransomware groups targeting VMware ESXi appliances. These attackers exploit vital virtual infrastructure to disrupt operations and remain hidden in compromised networks.
ESXi appliances have become prime targets due to their role in hosting vital virtual machines. “Damaging them renders virtual machines inaccessible, severely disrupting the business operations of affected organizations,” notes Sygnia.
UnitedHealth confirms 190 million impacted by 2024 data breach
Registration Open For BCS CTF 2025
New Ransomware Tactics Target VMware ESXi Via SSH Tunneling
Palo Alto Firewalls Found Vulnerable to Secure Boot Bypass
CISA Releases 6 ICS Advisories Detailing Security Issues
Account Credentials for Security Vendors Found on Dark Web: Cyble Report
Four Critical Ivanti CSA Vulnerabilities Exploited: CISA , FBI warns
GitLab Releases Patch (CVE-2025-0314) for XSS Exploit
CVE-2025-20156
Cisco Fixes Meeting Management Allowing Privilege Escalation
Delay patching leaves about 50,000 Fortinet firewalls to zero-day attack
Ransomware operators use ESXi devices to secretly tunnel malicious traffic within networks, often avoiding detection because of minimal monitoring.
The report highlights SSH tunneling as a tactic where attackers create a semi-persistent backdoor by using stolen admin credentials or vulnerabilities to access ESXi devices.
Threat actors use SSH to create a remote port-forwarding SOCKS tunnel, allowing them to mix malicious traffic with legitimate activity.
Sygnia explains, “Since ESXi appliances are resilient and rarely shutdown unexpectedly, this tunneling serves as a semi-persistent backdoor within the network.”
This method lets attackers avoid security measures and keep access for a long time.
ESXi’s logging structure complicates forensic investigations. Unlike traditional syslogs, ESXi organizes logs by activity, spreading critical events across multiple files, such as /var/log/shell.log, /var/log/auth.log, and /var/log/hostd.log. Sygnia emphasizes, “Configuring syslog forwarding from the ESXi server to an external syslog server can solve the issue.”
The report shows how Abyss Locker ransomware exploits ESXi appliances. Attackers exploited ESXi devices and NAS for network access, highlighting the importance of strong monitoring and defense strategies.
