A Scary Story of Group Policy Gone Wrong: Accidental Misconfigurations

In the world of cybersecurity, insider threats remain a potent and often underestimated danger. These threats can emanate not only from malicious actors within an organization but also from well-intentioned employees who inadvertently compromise security with a mis-click or other unwitting action. Having spent many years in system administrator-type roles, I’m actually surprised at how easy it remains for significant outages to come about, and the worst ones aren’t always the ones that cause huge blinking red lights initially but, in fact, are lingering silently in the background just waiting for an auditor – or worse, a criminal – to uncover.

Lest you think this sounds like a setup for an unnecessarily seasonal, Halloween-themed “IT horror” post, I wanted to share a tale of a real-world security incident that underscores why file integrity monitoring and regular compliance audits matter and can help you in thwarting insider threats, even when the threat is merely an accidental misconfiguration.

A Catastrophic Misconfiguration with all the best intentions

Imagine a large, multinational corporation with a vast network of servers powering its operations. This organization has diligently implemented stringent security measures, including robust audit logging on all servers to detect and investigate suspicious activities. These audit logs provide critical insights into who accessed what, when, and how, allowing the security team to respond promptly to potential threats, and quite rightly so, since the security and system operations teams depended upon these to stop risks in their tracks.

However, even the most comprehensive security measures can be rendered ineffective due to human error. In this case, a well-intentioned but inadvertently misguided system administrator was tasked with modifying Windows Group Policy settings across a significant portion of the organization’s servers. The intent was to enhance server performance and streamline operations, and the change request was easily approved.

Unbeknownst to the administrator, one seemingly innocuous change in the Windows Group Policy settings would have far-reaching consequences. In an attempt to reduce system resource usage, the administrator deployed an updated policy setting that modified only one small value, reducing the retention time for event log entries significantly and with the power of Group Policy quickly rolling out this new configuration, it took no time at all for this to quietly sweep away the breadcrumb trails that the admins had been using to complete root cause analyses, provide evidence to auditors, and assess ongoing security risks. These changes, while very much well-intentioned, inadvertently masked the organization’s ability to monitor user activities and security events effectively. Worse yet, no one knew that anything had changed…

The Quiet Aftermath

As days turned into weeks, the security team slowly started to notice a conspicuous silence in the audit logs from numerous servers. System administrators found it hard to track down errors they had assumed there would be clear evidence of. An application owner remarked that their application started behaving oddly due to a change in event volume, as well as the absence of historical logs that he couldn’t explain, as otherwise, all seemed well.

Alarms bells began to ring as they realized the gravity of the situation – the organization’s ability to detect, investigate, and respond to security incidents had been severely compromised and ironically also swept away a lot of the evidence that would have helped the team to understand just when the issue had started. It became painfully apparent that they were blind to the activities occurring on these servers.

FIM Shines a Light

Fortunately, the organization had a robust File Integrity Monitoring (FIM) system in place, with a separate auditing sub-system. This means that not only could they track down the change, but they could also understand when and why the change happened.

In this dire situation, the FIM system proved its worth. It promptly detected the changes to the Windows Group Policy settings on the affected servers, the user who had logged in and the script that was used. The security team, previously relying on log-based alerting, turned to the rich forensic data set collected by their FIM tool.

The puzzle pieces and the big picture

Once the misconfiguration was identified, the company didn’t take long to restore the audit logging settings to their previous state. While the incident had temporarily hindered their ability to monitor security events, the detection and remediation mitigated any potential long-term damage. Importantly, they also knew it wasn’t a malicious actor who had remained quietly on the network. They fully understood the events that led up to and following the misconfiguration. Indeed, they realised that a lot of the audit information the FIM tool was collecting could be correlated to other events they were still logging to help fill in the gaps for other security incidents.

They also learned their FIM tool could do more than just audit the log retention settings. It could check them against compliance standards, including their own (which added several new policy test requirements to ensure the availability and effectiveness of their log configurations) after the incident to reflect how critical those audit logs were. Not only would their FIM tool now help them evaluate such cases, but it could proactively warn them of an issue about to happen.

I retell this story regularly during Tripwire Enterprise (TE) engagements because it’s often familiar to many who get started in support roles and understand the importance of logging and how even the smallest of errors can be a nightmare to unravel without the right tools. With a robust FIM program in place, TE’s agents can act as vigilant sentinels, promptly detecting any unauthorized changes to critical files and settings and catching what other tools can’t, even when native OS auditing might fail you. This is another reason why integrity management is about so much more than just alerting; it’s about ensuring you’ve got the full picture when you need it the most.