LESSON 1.1: ZEEK ECOSYSTEM OVERVIEW
PART 1: THE EVOLUTION OF ZEEK - FROM RESEARCH PROJECT TO ENTERPRISE STAPLE
The Birth of Something Different
In 1995, a PhD student at UC Berkeley named Vern Paxson was working on his dissertation at Lawrence Berkeley National Laboratory. The laboratory had a problem that was becoming increasingly common in the mid-1990s: their network was under constant probing and attack, but existing intrusion detection systems weren’t giving them the visibility they needed. These systems, which primarily relied on signature matching, could tell you if a known attack pattern appeared in your traffic, but they couldn’t tell you much about what was actually happening on the network moment to moment.
Paxson approached the problem differently. Instead of building yet another signature-matching system, he asked himself: “What if we built a system that could continuously observe network activity, understand the protocols being used, track the state of connections, and provide a rich stream of information about what’s really happening?” This question led to the creation of Bro - originally standing for “Big Brother,” a reference to Orwell’s all-seeing surveillance system, though in this case watching networks rather than people.
The early version of Bro that emerged from Paxson’s research had several revolutionary characteristics that set it apart from everything else available at the time. First, it was designed to be completely passive. Rather than sitting inline and potentially becoming a bottleneck or single point of failure, Bro would observe a copy of network traffic without interfering with it. Second, it separated policy from mechanism. The core engine would handle the hard work of parsing protocols and tracking connection state, while separate scripts - written in a custom scripting language - would implement the detection logic. This meant that security analysts could customize detection behaviour without modifying the core system.
Third, and perhaps most importantly, Bro was designed to generate rich logs about network activity whether or not any suspicious behaviour was detected. This was a radical departure from traditional intrusion detection systems, which primarily generated alerts when signature matches occurred. Paxson understood that for real network security monitoring, you needed to understand baseline behavior, track long-term trends, and have detailed forensic data available when investigating incidents.
From Academic Tool to Production System
Throughout the late 1990s and early 2000s, Bro was primarily deployed in academic and research environments. Universities and national laboratories were ideal environments for the tool because they had the technical expertise to manage it and appreciated its flexibility and depth. But Bro was not an easy system to deploy. It required significant expertise to configure, tune, and operate effectively. The scripting language was powerful but had a steep learning curve. The system generated enormous volumes of logs that needed to be managed and analyzed.
Despite these challenges, organizations that invested in deploying Bro discovered something remarkable: they could detect sophisticated attacks that their signature-based systems completely missed. When an attacker used a novel technique or modified existing malware to evade signatures, Bro’s behavioural analysis capabilities could still identify anomalous activity. A connection that established itself and then sat open for hours sending periodic small packets might look innocuous to a signature-based system, but Bro could identify it as potential command-and-control traffic based on its behavioural characteristics.
As Bro matured through the 2000s and early 2010s, several major improvements expanded its capabilities. The introduction of cluster architecture meant that Bro could scale to monitor high-bandwidth networks by distributing the analysis workload across multiple systems. The development of the Broker communication framework provided efficient mechanisms for different Bro instances to share data and coordinate analysis. The scripting language evolved to support more sophisticated detection logic and statistical analysis.
By 2013, when Bro reached version 2.0, it had become a production-grade system capable of monitoring some of the world’s most demanding networks. But it still carried the “Bro” name, which was increasingly seen as a barrier to broader adoption. Some organizations were hesitant to deploy a security tool with a name that could be seen as unprofessional or insensitive.
The Transformation to Zeek
In October 2018, the Bro project announced that it would be rebranding to Zeek. The name, derived from the prophet Ezekiel who had visions of future events, symbolized the system’s ability to provide foresight into network threats through its analytical capabilities. More practically, the name change was part of a broader effort to make the project more accessible and welcoming to a wider audience.
The rebranding to Zeek marked more than just a name change. It represented a maturation of the project from a research tool with an academic pedigree into a system that organizations of all types could adopt. The documentation was improved and reorganized. The package management system was enhanced to make it easier to discover and install community-contributed scripts. Commercial support options became available through companies like Corelight, which was founded by the original Zeek developers.
Today, Zeek is deployed in environments ranging from small businesses to Fortune 500 companies, from university networks to critical infrastructure providers. It’s used by government agencies for national security missions and by managed security service providers offering network monitoring services to their clients. The tool that began as one graduate student’s research project has become a cornerstone of modern network security monitoring.