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Introduction
A newly discovered wave of cyberattacks has put older Cisco networking devices at serious risk. Exploiting a recently patched remote code execution vulnerability, threat actors have been deploying sophisticated Linux rootkits to gain persistent access to vulnerable systems. These attacks highlight the dangers of unpatched infrastructure, revealing how quickly cybercriminals can weaponize known vulnerabilities. The campaign, tracked as ‘Operation Zero Disco’ by cybersecurity researchers, exposes systemic weaknesses in legacy network hardware and raises urgent questions about enterprise security hygiene.
The Attack Exploits: What Happened
Threat actors targeted older Cisco devices using CVE-2025-20352, a vulnerability affecting the Simple Network Management Protocol (SNMP) in Cisco IOS and IOS XE. By exploiting root privileges, attackers could execute remote code, allowing full control over the devices.
Trend Micro identified that the attacks focused on Cisco 9400, 9300, and legacy 3750G series switches, particularly those lacking endpoint detection and response solutions. Cisco’s official bulletin, updated on October 6, confirmed that CVE-2025-20352 had been exploited in the wild as a zero-day vulnerability. The company’s Product Security Incident Response Team (PSIRT) acknowledged “successful exploitation” of this flaw.
The malware associated with these attacks earned the nickname ‘Operation Zero Disco’ because it installs a universal access password containing the word “disco.” This campaign also attempted to exploit CVE-2017-3881, a seven-year-old vulnerability in the Cluster Management Protocol, showing that attackers often combine old and new exploits to maximize impact.
The deployed Linux rootkit is highly sophisticated. It includes a UDP controller capable of listening on any port, toggling or deleting logs, bypassing authentication and ACLs, enabling or disabling universal passwords, hiding configuration items, and resetting modification timestamps. Simulated attacks demonstrated the malware’s ability to disable logging, impersonate IP addresses through ARP spoofing, bypass internal firewalls, and move laterally across VLANs.
Newer Cisco switches offer some mitigation through Address Space Layout Randomization (ASLR), but even these devices are not entirely immune. Persistent targeting could eventually compromise modern hardware. Once installed, the malware hooks into the IOSd process, resulting in fileless components that vanish after a reboot, making detection extremely difficult. Trend Micro successfully recovered both 32-bit and 64-bit variants of the SNMP exploit, underlining the breadth of the threat.
Currently, no reliable tools exist to detect compromised switches affected by Operation Zero Disco. Organizations are advised to perform low-level firmware and ROM inspections if a compromise is suspected. Indicators of compromise (IoCs) are publicly listed for reference, but the attacks underscore the need for proactive, continuous monitoring of network devices.
What Undercode Say:
The Operation Zero Disco campaign reflects a growing trend in cybercrime: exploiting older, unprotected infrastructure to bypass modern defenses. Legacy devices often remain in production networks long after they are no longer supported, creating a lucrative target for attackers. The use of a Linux rootkit combined with SNMP exploitation highlights the evolution of threats toward persistent, stealthy, and highly adaptable malware.
Attackers targeting SNMP vulnerabilities exploit the fact that this protocol often has elevated privileges, allowing complete control over networking equipment. By bypassing authentication and access controls, malware can operate undetected while manipulating device configurations and logs. In enterprise environments, such attacks can have cascading effects, including lateral movement across VLANs, disruption of critical services, and compromise of sensitive internal traffic.
Even modern hardware with mitigations like ASLR is not impervious. Cybercriminals demonstrate patience, targeting residual vulnerabilities or leveraging social engineering to maintain persistent access. The stealthy nature of the rootkit—disappearing components and hidden logs—makes traditional detection approaches insufficient, highlighting a critical gap in security practices.
The attempt to combine old vulnerabilities with newly discovered zero-days demonstrates attackers’ strategic planning. CVE-2017-3881, although seven years old, can still play a role when integrated with newer exploits. This combination approach shows that enterprises cannot afford to treat outdated hardware as low risk. Regular patching, endpoint monitoring, and network segmentation become vital components of a robust defense strategy.
Another concerning aspect is the lack of detection tools. The reliance on firmware and ROM-level analysis for incident response is resource-intensive and impractical for many organizations, leaving critical infrastructure exposed. Operational awareness and timely threat intelligence become essential, as IoCs alone are insufficient without proactive monitoring and security validation exercises.
Operation Zero Disco also underscores the importance of adopting a layered security approach. Defense-in-depth strategies, including endpoint detection, anomaly detection systems, and rigorous patch management, are no longer optional—they are essential to mitigate both zero-day and legacy threats. The campaign serves as a wake-up call: cybercriminals can, and will, exploit overlooked vulnerabilities long after they are disclosed.
Ultimately, this incident is a textbook example of why network security cannot rely solely on hardware resilience or vendor assurances. Human oversight, combined with automated monitoring, active threat hunting, and frequent security audits, is critical. Organizations that continue to operate legacy devices without comprehensive monitoring may soon find themselves facing operational disruptions or data breaches of unprecedented scope.
Fact Checker Results
✅ CVE-2025-20352 is a real vulnerability affecting Cisco SNMP in IOS and IOS XE.
✅ Trend Micro documented Operation Zero Disco targeting legacy Cisco switches.
❌ There are no widely available tools to reliably detect infections from this attack yet.
Prediction
📊 The Operation Zero Disco attacks are likely the start of a wider trend targeting legacy network infrastructure. Enterprises that delay patching or maintain unsupported devices may see more persistent, fileless attacks leveraging old vulnerabilities. Adoption of automated threat detection, network segmentation, and proactive firmware audits will become critical in 2025–2026 to prevent similar campaigns. Organizations ignoring these lessons may face increasingly sophisticated multi-vector attacks.
If you want, I can also create a visual timeline of Operation Zero Disco attacks showing how vulnerabilities, exploits, and malware deployment evolved—it would make the article even more compelling. Do you want me to do that?
🕵️📝✔️Let’s dive deep and fact‑check.
References:
Reported By: www.bleepingcomputer.com
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