Click here to close now.


Microservices Expo Authors: Liz McMillan, Elizabeth White, SmartBear Blog, Pat Romanski, Ruxit Blog

Related Topics: Cloud Security, Industrial IoT, Microservices Expo, Adobe Flex, Agile Computing

Cloud Security: Article

Capture File Filtering with Wireshark

Needle in a Haystack

Intrusion detection tools that use the libpcap C/ C++ library [1] for network traffic capture (such as Snort [2] and Tcpdump [1]) can output packet capture information to a file for later reference. The format of this capture file is known as pcap. By capturing packet data to a file, an investigator can return later to study the history of an intrusion attempt – or to turn up other important clues about clandestine activity on the network.

Of course, the traffic history data stored in a pcap file is much too vast to study by just viewing the file manually. Security experts use specialized filtering tools to search through the file for pertinent information. One way to look for clues in a pcap file is to use the Wireshark protocol analysis tool [3] and its accompanying command-line utility tshark.

Wireshark is included by default on many Linux distros, and if not, it is available through the leading package repositories. You can also download Wireshark through the project website [4]. In this article, I describe how to use Wireshark and tshark to search a pcap file for information on network activity. I will assume you already have a pcap file ready for investigation. For more on how to capture a pcap file with Tcp-dump, see my article “Intruder Detection with Tcpdump,” which is available online at the ADMIN magazine website [5].

tshark at the Command Line
The tshark utility is a simple tool included with the Wireshark package that lets you filter the contents of a pcap file from the command line. To get a view of the most significant activity, I use the following command:

$ tshark ‑nr dumpfile1.gz ‑qz "io,phs" > details.txt

The ‑n switch disables network object name resolution, ‑r indicates that packet data is to be read from the input file, in this case dumpfile1.gz. The ‑z allows for statistics to display after it finishes reading the capture file, the ‑q flag specifies that only the statistics are printed, and the > redirection
sends the output to the file called details.txt. See Figure 1 for the output of this information. To view a list of help commands used with tshark, type:

$ tshark ‑h

And for a list of ‑z arguments type:

$ tshark ‑z help

Figure 1

Say you would like to know whether a particular IP address appeared in a packet dump and what port it was connecting on. The following command line checks the dump file for the IP address

$ tshark ‑V ‑nr dumpfile.gz ip.src == | grep "Source port" | awk {'print $3'} | sort ‑n | uniq 80

The resulting output on the line following the command shows that the packet dump file recorded IP address having connections on port 80.

If you were given a packet dump file and asked to find possible IRC traffic on your network, how would you do it? First, you would need to know what port numbers were associated with IRC traffic, and that could be accomplished with Google or by issuing the following command:

$ grep irc /usr/share/nmap/nmap‑services | grep tcp

Figure 2 shows the results of the preceding command.

Figure 2

Now I can search the packet dump and look for evidence of IRC traffic using the following commands:

$ tshark ‑nr dumpfile1.gz 'ip.addr== and tcp.port >=  6667 and tcp.port <= 6670 and irc' |  awk {'print $3,$4,$5,$6'} | sort ‑n | uniq ‑c

Figure 1: tshark statistics output.
Figure 2: Locating IRC port numbers with grep.
Figure 3: IRC connections found in the packet dump.
Figure 4: The Wireshark startup window.

The breakdown of this command is shown in Table 1, and the output is in Figure 3.

Figure 3

In the GUI
The Wireshark GUI application is easier on the eyes, and it provides some options that aren’t available at the command line. You can start Wireshark from the Application menu or from the terminal.  To load a capture file, select Open in the startup window (Figure 4) or select File | Open from the menubar.  Once you have a packet capture file loaded, you can start searching packet dumps within the Wireshark interface.

Figure 4

The Filter box below the Wireshark toolbar lets you enter criteria for the search. For instance, to search for all the Canonical Name records within the capture file, type in the following filter: dns.resp.type == CNAME (see Figure 5).  After you enter a filter, remember to clear the filter text to see the full file before starting a new search.

Figure 5

Table 1: Parts of a tshark Command

Option Description
‘ip.addr==         This is my network
and tcp.port >= 6667                   Start of the port range
and tcp.port <= 6670                   End of the port range
and irc’                                           Searches for IRC traffic only
awk {‘print $3,$4,$5,$6’}             Prints the third through sixth patterns from each matching line
sort ‑n                                            Sorts according to string numerical value
uniq ‑c                                            Only prints the number of matches that are unique

Digging deeper, if I want to know how long a client resolver cached the IP address associated with the name (Figure 6), I would enter the following filter: == "cookex.amp.gapx."

Figure 6

The filter ip.addr == gives information on all communications that involve in the packet dump. If needed, use && to isolate to a specific protocol. The filter ip.dst == or ip.src == looks for a source or destination IP address.

How could I find the password used over Telnet between two IP addresses? For example, if a user at is using Telnet to access a device at 10. 37. 140.160, I can enter:

ip.dst == && ip.src == && contains "Password"

The preceding command will list the connections that meet the search requirement, and you can right-click on the packet and click Follow TCP Stream to view the password. (See Figures 7 and 8.)

Figure 7

Figure 8

Note: A much easier way to get the password on the network, if you were sniffing the traffic instead of reading from a capture file, would be to use ettercap, as follows:

$ ettercap ‑Tzq //23

To discover whether someone was viewing a suspicious web page, I can perform a filter search to find out what picture the person at IP address was viewing at Yahoo ( with the following filter:

ip.dst == && ip.src == && (image‑jfif || image‑gif)

Figure 9

Figure 9 shows the results. If you then right-click on a line in the output and select Follow TCP Stream for the results shown in Figure 10.
The second line in the Follow TCP Stream output specifies that wynn‑ rovepolitico.jpg is the image this person was viewing on the site.

Figure 10

Wireshark can do more than just watch the wires in real time. If you save a snapshot of network activity in a capture file in the pcap format, you can use Wireshark to search through the file to look for clues about nefarious activity.

In this article, I described how to search for information in a capture file using Wireshark and the tshark command-line tool.


[1] Tcpdump and Libpcap:
[2] Snort:
[3] Wireshark:
[4] Wireshark Download:
[5] “Intruder Detection with Tcpdump” by David J. Dodd: http://www.admin‑‑Detection‑with‑tcpdump/

More Stories By David Dodd

David J. Dodd is currently in the United States and holds a current 'Top Secret' DoD Clearance and is available for consulting on various Information Assurance projects. A former U.S. Marine with Avionics background in Electronic Countermeasures Systems. David has given talks at the San Diego Regional Security Conference and SDISSA, is a member of InfraGard, and contributes to Secure our eCity He works for Xerox as Information Security Officer City of San Diego & pbnetworks Inc. a Service Disabled Veteran Owned Small Business (SDVOSB) located in San Diego, CA and can be contacted by emailing: dave at

@MicroservicesExpo Stories
It’s been proven time and time again that in tech, diversity drives greater innovation, better team productivity and greater profits and market share. So what can we do in our DevOps teams to embrace diversity and help transform the culture of development and operations into a true “DevOps” team? In her session at DevOps Summit, Stefana Muller, Director, Product Management – Continuous Delivery at CA Technologies, answered that question citing examples, showing how to create opportunities for ...
Whether you like it or not, DevOps is on track for a remarkable alliance with security. The SEC didn’t approve the merger. And your boss hasn’t heard anything about it. Yet, this unruly triumvirate will soon dominate and deliver DevSecOps faster, cheaper, better, and on an unprecedented scale. In his session at DevOps Summit, Frank Bunger, VP of Customer Success at ScriptRock, will discuss how this cathartic moment will propel the DevOps movement from such stuff as dreams are made on to a prac...
SYS-CON Events announced today that DataClear Inc. will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. The DataClear ‘BlackBox’ is the only solution that moves your PC, browsing and data out of the United States and away from prying (and spying) eyes. Its solution automatically builds you a clean, on-demand, virus free, new virtual cloud based PC outside of the United States, and wipes it clean...
In his session at 17th Cloud Expo, Ernest Mueller, Product Manager at Idera, will explain the best practices and lessons learned for tracking and optimizing costs while delivering a cloud-hosted service. He will describe a DevOps approach where the applications and systems work together to track usage, model costs in a granular fashion, and make smart decisions at runtime to minimize costs. The trickier parts covered include triggering off the right metrics; balancing resilience and redundancy ...
Culture is the most important ingredient of DevOps. The challenge for most organizations is defining and communicating a vision of beneficial DevOps culture for their organizations, and then facilitating the changes needed to achieve that. Often this comes down to an ability to provide true leadership. As a CIO, are your direct reports IT managers or are they IT leaders? The hard truth is that many IT managers have risen through the ranks based on their technical skills, not their leadership ab...
Several years ago, I was a developer in a travel reservation aggregator. Our mission was to pull flight and hotel data from a bunch of cryptic reservation platforms, and provide it to other companies via an API library - for a fee. That was before companies like Expedia standardized such things. We started with simple methods like getFlightLeg() or addPassengerName(), each performing a small, well-understood function. But our customers wanted bigger, more encompassing services that would "do ...
SYS-CON Events announced today that Pythian, a global IT services company specializing in helping companies leverage disruptive technologies to optimize revenue-generating systems, has been named “Bronze Sponsor” of SYS-CON's 17th Cloud Expo, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Founded in 1997, Pythian is a global IT services company that helps companies compete by adopting disruptive technologies such as cloud, Big Data, advance...
Early in my DevOps Journey, I was introduced to a book of great significance circulating within the Web Operations industry titled The Phoenix Project. (You can read our review of Gene’s book, if interested.) Written as a novel and loosely based on many of the same principles explored in The Goal, this book has been read and referenced by many who have adopted DevOps into their continuous improvement and software delivery processes around the world. As I began planning my travel schedule last...
Docker containerization is increasingly being used in production environments. How can these environments best be monitored? Monitoring Docker containers as if they are lightweight virtual machines (i.e., monitoring the host from within the container), with all the common metrics that can be captured from an operating system, is an insufficient approach. Docker containers can’t be treated as lightweight virtual machines; they must be treated as what they are: isolated processes running on hosts....
What does “big enough” mean? It’s sometimes useful to argue by reductio ad absurdum. Hello, world doesn’t need to be broken down into smaller services. At the other extreme, building a monolithic enterprise resource planning (ERP) system is just asking for trouble: it’s too big, and it needs to be decomposed.
SYS-CON Events announced today that G2G3 will exhibit at SYS-CON's @DevOpsSummit Silicon Valley, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Based on a collective appreciation for user experience, design, and technology, G2G3 is uniquely qualified and motivated to redefine how organizations and people engage in an increasingly digital world.
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
SYS-CON Events announced today the Containers & Microservices Bootcamp, being held November 3-4, 2015, in conjunction with 17th Cloud Expo, @ThingsExpo, and @DevOpsSummit at the Santa Clara Convention Center in Santa Clara, CA. This is your chance to get started with the latest technology in the industry. Combined with real-world scenarios and use cases, the Containers and Microservices Bootcamp, led by Janakiram MSV, a Microsoft Regional Director, will include presentations as well as hands-on...
The pricing of tools or licenses for log aggregation can have a significant effect on organizational culture and the collaboration between Dev and Ops teams. Modern tools for log aggregation (of which Logentries is one example) can be hugely enabling for DevOps approaches to building and operating business-critical software systems. However, the pricing of an aggregated logging solution can affect the adoption of modern logging techniques, as well as organizational capabilities and cross-team ...
In today's digital world, change is the one constant. Disruptive innovations like cloud, mobility, social media, and the Internet of Things have reshaped the market and set new standards in customer expectations. To remain competitive, businesses must tap the potential of emerging technologies and markets through the rapid release of new products and services. However, the rigid and siloed structures of traditional IT platforms and processes are slowing them down – resulting in lengthy delivery ...
Skeuomorphism usually means retaining existing design cues in something new that doesn’t actually need them. However, the concept of skeuomorphism can be thought of as relating more broadly to applying existing patterns to new technologies that, in fact, cry out for new approaches. In his session at DevOps Summit, Gordon Haff, Senior Cloud Strategy Marketing and Evangelism Manager at Red Hat, discussed why containers should be paired with new architectural practices such as microservices rathe...
Any Ops team trying to support a company in today’s cloud-connected world knows that a new way of thinking is required – one just as dramatic than the shift from Ops to DevOps. The diversity of modern operations requires teams to focus their impact on breadth vs. depth. In his session at DevOps Summit, Adam Serediuk, Director of Operations at xMatters, Inc., will discuss the strategic requirements of evolving from Ops to DevOps, and why modern Operations has begun leveraging the “NoOps” approa...
Puppet Labs has announced the next major update to its flagship product: Puppet Enterprise 2015.2. This release includes new features providing DevOps teams with clarity, simplicity and additional management capabilities, including an all-new user interface, an interactive graph for visualizing infrastructure code, a new unified agent and broader infrastructure support.
DevOps has traditionally played important roles in development and IT operations, but the practice is quickly becoming core to other business functions such as customer success, business intelligence, and marketing analytics. Modern marketers today are driven by data and rely on many different analytics tools. They need DevOps engineers in general and server log data specifically to do their jobs well. Here’s why: Server log files contain the only data that is completely full and accurate in th...
The Microservices architectural pattern promises increased DevOps agility and can help enable continuous delivery of software. This session is for developers who are transforming existing applications to cloud-native applications, or creating new microservices style applications. In his session at DevOps Summit, Jim Bugwadia, CEO of Nirmata, will introduce best practices, patterns, challenges, and solutions for the development and operations of microservices style applications. He will discuss ...