Over the past few weeks, I have been experimenting with the latest form of spycraft, though it was hardly what I was expecting. Sometime around the 1980s, the military and intelligence organizations started to allocate at least some of their covert resources away from traditional spying activities like embedding agents and trying to hack into classified networks. Instead, some resources were devoted to scanning public sources of information like newspapers and official documents. This kind of spycraft was dubbed open source intelligence gathering, or OSINT for short.

OSINT efforts got a big boost with the rise of the internet and then another huge one when social media went mainstream. Skilled intelligence agents no longer have to always cultivate sources in rival governments or perform dangerous operations in unfriendly territory. Instead, they can sometimes get just as valuable information by connecting the dots and linking several publicly available information snippets into a much larger picture. It’s still a lot of work, but mostly conducted from the safety of a computer terminal sitting at their office.

To speed up the data collection process, OSINT automation tools were created. They could be directed to collect general information about a topic or even tasked with answering specific questions using publicly accessible information. People realized over time that they could turn those same tools inward, checking to see if friendly organizations were accidentally sharing sensitive or secret information themselves. CSO Magazine asked me to evaluate several of the top OSINT tools available today, and it was quite an interesting experience.

There are two things that I found most surprising about OSINT tools. The first is that many of them are available for free, created by developers who want to help with open source intelligence gathering. A few companies also offer a free version of their OSINT tool and then a paid version with more advanced features. Having that kind of power provided for free was a little shocking.

And secondly, most people don’t apply OSINT tools to spycraft. Instead, they are used to improve cybersecurity. Think about it like this: Every agency has a vast public-facing infrastructure that can reach across multiple physical networks and into the cloud. Their namespaces and hosting services share information. Some agencies additionally have employees using personal devices as part of a BYOD program. Even things like security cameras and Internet of Things devices might share little snippets of data to whoever happens to ask for it. There could even be potentially compromising information available in the source code of an agency’s active programs and applications. And all of that is just considering assets that agencies directly control.

When you expand an OSINT search to look at outside assets such as social media channels, the potential of an intelligence windfall for an attacker becomes even greater. Skillfully using an OSINT tool to locate sensitive information before an attacker (or a spy) means being able to remove, hide or protect that data before it can be mined to create something like a phishing scam attacking employees, or used to target your network directly.

All of the OSINT tools looked at were easy to use. In a few cases, it was no more difficult than working with an advanced search engine. For example, a tool called theHarvester is available for free on GitHub. It’s designed to capture public information about an agency that exists outside of the networks that they directly control. It uses both normal search engines like Bing and Google, as well as lesser known sources like DNSdumpster, the Exalead metadata engine and Dogpile. Most of the information it gathered during my testing related to emails, usernames, subdomains (including inactive and forgotten ones), IP addresses and URLs.

A more advanced OSINT tool called Maltego did a surprisingly good job of connecting the dots, taking seemingly disparate information snippets from multiple sources and tying them together into a complete picture of actionable intelligence. It even helps users to visualize the scope of the problem by putting discovered intelligence fragments together on a graph with up to 10,000 data points to show how it all relates to one another. You have to pay to use the premium Maltego XL program, but a desktop version is available for free if you want to try out the technology.

A few OSINT programs I examined specialized in specific aspects of intelligence gathering. For example, Shodan looks at the Internet of Things as well as operational technology devices found in places like power plants and the utilities industry. Metagoofil is optimized to pull hidden metadata from public documents. Simply point it at PDFs, Word files, PowerPoint slides, Excel spreadsheets or almost any document repository, and it will ferret out things like the names of authors and editors who worked on them, even if that information was not specifically disclosed.

OSINT tools are powerful because they can uncover a lot of hidden, sensitive or even potentially classified information without having to resort to hacking or any other illegal activity. Those charged with improving cybersecurity at agencies should certainly give some of them a try, as it’s an eye-opening experience. And the actionable intelligence they find can be used to plug security loopholes well before an attacker can connect the dots and launch an attack.

John Breeden II is an award-winning journalist and reviewer with over 20 years of experience covering technology. He is the CEO of the Tech Writers Bureau, a group that creates technological thought leadership content for organizations of all sizes. Twitter: @LabGuys