<i>Tech Insight</i>: Free Network Tool Shows The Bigger Picture

A Special Analysis for Dark Reading

It can take hours or days to truly understand what took place during a security incident. Security analysts and forensics investigators try to put IDS alerts, system logs, and user reports into context to determine if an attack was successful, if sensitive data really did leave the network, and other tough questions. Tools like Wireshark, tcpdump, ngrep, and snort are the bread-and-butter during these times of intense analysis. But things are about to change -- for the better.

Earlier this week, NetWitness released a free version of its Investigator network analysis tool. Investigator gives you contextual analysis of raw network data and allows analysts to step back and view it all at the session-level as opposed to the packet level, like Wireshark.

I recently used Investigator for the better part of a day, analyzing packets captured directly from a production network, as well as previously captured packets from the DefCon Capture the Flag contest. Investigator does a great job of breaking out the individual sessions and providing metadata about sessions that lets you dive deeper simply by clicking on the different items, such as TCP, HTTP, MAC, Source IP, and even Location.

Does this mean you should toss aside Wireshark and your other tools? Absolutely not. NetWitness Investigator is a complementary tool, not a replacement. Investigator lets you look at billions of packets and flows and analyze them more quickly and easily, says Tim Belcher, NetWitness' CTO. It turns the billions of packets into thousands of sessions, he says, and then you can use Wireshark to drill down even more deeply.

The best way to differentiate Wireshark and Investigator is how security expert Richard Bejtlich explained in his "Network Forensics with NetWitness" blog entry. Wireshark is already known as one of the best network protocol analyzers around, but Richard notes that it's a packet-centric tool, and that Investigator is data-centric.

For example, separating sessions in Wireshark can be tedious and slow. Once an item of interest has been identified, clicking on "Follow TCP Session" provides that single session, but stops there. The session content cannot be viewed natively within Wireshark as a Web page if it is a Web browsing session, nor as an image if it were a picture viewed on Flickr. It has to be exported first and then opened with the relevant application.

Investigator, meanwhile, does all of the session reconstruction and presentation natively for you. When you click on an HTTP session in Investigator, it presents a thumbnail view that can be zoomed in to see the full Web page and any embedded graphics. The same goes for e-mail. And I found that its speed is impressive, too: Clicking around the interface and drilling down into the different sessions was incredibly fast compared with searching and filtering the same data in Wireshark. NetWitness' demonstration video (on YouTube or HD) shows examples of this, as the presenter navigates through the interface.

What's the catch? NetWitness obviously wants to get its name out there and show off what it can do to entice you to look at its enterprise network forensic products. Of course, this isn't the first time a vendor has taken this approach to get some instant exposure. And you'll find NetWitness has some other solutions that may fit well within your organization.

So the company must have crippled Investigator before releasing it for free, right? Not so. The only limitation is that capturing live data and reading previously captured network data is restricted to a size of 1 GB. And it can only open up to 25 previously captured files at a time. So to recap, Investigator can read up to 25 GB of network traffic spread across 25 1-GB files; that's no handicap, nor is it something that Wireshark can do.

NetWitness Investigator is a tool that's going to stick around and probably become one of the more popular tools for better understanding the bigger picture and placing an event of interest into context. Wireshark will still have a home in every security professional's toolkit, too. Only now, it has a big brother to look up to.

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