Overview
On New Year’s Day, Microsoft released a Defender antivirus definition update that incorrectly flagged a legitimate N-Able management file, softwarescanner.exe, as a potential threat. This false positive triggered a global ripple effect as other security tools followed Microsoft’s lead. The impact varied depending on each customer’s configuration. In Mechdyne‑managed environments, the issue was identified not by Microsoft Defender but by SentinelOne, which reacted to the definition update by quarantining the file and placing the device in network lock; restricting all inbound and outbound traffic to protect the rest of the corporate network. As the incident began unfolding worldwide, Mechdyne’s technical teams immediately took action to protect client environments, assess the scope of the situation, and restore normal functionality as quickly as possible so clients avoided costly downtime.
Challenge
The update caused security software to quarantine or block critical N-Able management components by placing affected machines into network quarantine. This action leverages the device’s software firewall to block all inbound and outbound traffic, effectively cutting the device off from the internet and all company resources. From the user’s perspective, the computer appeared offline and unusable; they could not browse, work, or access any internal services.
Despite this, Mechdyne still had limited connectivity to manage devices because one port remains open for remote management. The complexity of the situation was compounded by early uncertainty: Was this simply a false positive, or was it the beginning of a supply chain attack? With businesses around the globe reporting the same issue on cybersecurity forums and vendor channels, the urgency of responding, especially on a holiday evening, was immediately clear.
Solution
Mechdyne’s response began with monitoring activity. Because our team continuously watches client environments, we detected alerts as soon as they appeared and initiated investigation within minutes, despite it being the evening of New Year’s Day.
The team monitored global cybersecurity communities and vendor alerts to understand the full scope. Reports from the cybersecurity and sysadmin subreddits, combined with updates from N-Able, confirmed that this was a widespread issue affecting organizations using the N-Able and Microsoft Defender/SentinelOne combination.
Next, Mechdyne carefully verified the integrity of the affected files with N-Able, since only the vendor could confirm whether the flagged hash was legitimate. Early on, there was no way to be certain the file hadn’t been tampered with. As a result, the team intentionally held off bringing quarantined machines back online until they had positive confirmation from N-Able that the detection was indeed a false positive.
Once confirmed, the team coordinated with vendors, implemented corrective actions, and restored full functionality across impacted devices, ensuring safety and stability throughout the process.
Outcome
Because Mechdyne’s teams were monitoring client environments, we were able to respond within minutes of the issue appearing. SentinelOne’s quick action led to rapid identification and containment, protecting client data and keeping every environment fully secure.
Even though the incident occurred on a holiday evening, Mechdyne demonstrated its commitment to 24/7 vigilance by mobilizing immediately, coordinating with vendors, and resolving the issue safely. The response not only minimized downtime but also reinforced client trust through clear communication, protective decision making, and strong technical expertise during a global security event.