RawCap Redux

A new version of RawCap has been released today. This portable little sniffer now supports writing PCAP data to stdout and named pipes as an alternative to saving the captured packets to disk. We have also changed the target .NET Framework version from 2.0 to 4.7.2, so that you can run RawCap on a modern Windows OS without having to install a legacy .NET Framework.

Here’s a summary of the improvements in the new RawCap version (0.2.0.0) compared to the old version (0.1.5.0):

• Uses .NET 4.7.2 instead of 2.0
• Support for writing to stdout
• Support for writing to named pipes
• Large (64 MB) ring buffer to prevent packet drops
• Automatic firewall configuration

Out of the software we develop and maintain here at Netresec, NetworkMiner is the most popular one. But you’re probably not aware that RawCap is our second most popular tool in terms of downloads, with around 100 unique downloads every day. RawCap started out as just being a quick hack that we released for free to the community in 2011 without expecting it to gain much attention. However, it quickly gained popularity, maybe due to the fact that it’s just a tiny .exe file and that it doesn’t require any external libraries or DLL’s to sniff network traffic (other than the .NET Framework).

RawCap embraces the Unix philosophy to do only one thing, and do it well. Thanks to RawCap’s simplicity we have only needed to make a few minor updates of the tool since its first release 9 years ago. However, today we’re finally adding some new features that have been requested by users over the years. One such feature is that RawCap now automatically creates a Windows firewall rule when the tool is started. Before this feature was introduced users would have to run wf.msc (i.e. the "Windows Defender Firewall with Advanced Security") and manually create an inbound rule to allow RawCap.exe to receive incoming traffic. Without such a firewall rule RawCap would only be able to capture outgoing traffic.

RawCap can be started in two different modes. Either as an interactive console application, or as a “normal” command line utility. Run RawCap.exe without any arguments, or simply double click the RawCap.exe icon to use the interactive mode. You will then be asked which interface to capture packets from and what filename you’d like to save them to.

The other alternative is to supply all the arguments to RawCap when it is started. Use “RawCap --help” to show which arguments you can use. You’ll need to use this mode if you want to write the captured traffic to standard output (stdout) or a named pipe, or if you want RawCap to automatically stop capturing after a certain time or packet count.

As you can see, running “RawCap.exe -s 60 127.0.0.1 localhost.pcap” will capture packets from localhost to a file called “localhost.pcap” for 60 seconds and then exit.

There are a couple of drawbacks with the new RawCap version though, it is a larger binary (48kB instead of 23kB) and it uses more CPU and RAM compared to the old version. We will therefore continue making the old RawCap version available to anyone who might need it.

Visit the RawCap product page to download this tool and learn more.

Posted by Erik Hjelmvik on Thursday, 30 January 2020 14:32:00 (UTC/GMT)

Tags: #Netresec​ #RawCap​ #sniffer​ #PCAP​ #named pipe​ #Wireshark​ #WiFi​ #loopback​ #127.0.0.1​

PacketCache lets you Go Back in Time

Have you ever wanted to go back in time to get a PCAP of something strange that just happened on a PC?
I sure have, many times, which is why we are now releasing a new tool called PacketCache. PacketCache maintains a hive of the most important and recent packets, so that they can be retrieved later on, if there is a need.

Network forensics and incident response is performed post-event, but requires that packet have already been captured during the event to be analyzed. Starting a network sniffer after a suspected intrusion might provide useful insight on what the intruders are up to, but it is much better to be able to go back in time to observe how they gained access to the network and what they did prior to being detected. Many companies and organizations combat this problem by setting up one or several solutions for centralized network packet capturing. These sniffers are typically installed at choke-points on the network, such as in-line with a firewall. However, this prevents the sniffers from capturing network traffic going between hosts on the same local network. Intruders can therefore often perform lateral movement on a compromised network without risk getting their steps captured by a packet sniffer.

Image by Game Gavel

By default PacketCache reserves 1% of a computer's total physical memory for storing packets. A computer with 4 GB of RAM will thereby allow up to 40 MB of packets to be kept in memory. This might not seem like much, but PacketCache relies on a clever technique that allows it to store only the most important packets. With this technique just 40 MB of storage can be enough to store several days worth of “important” packets.

The “clever technique” we refer to is actually a simple way of removing packets from TCP and UDP sessions as they get older. This way recent communication can be retained in full, while older data us truncated at the end (i.e. only the last packets are removed from a session).

To download PacketCache or learn more about this new tool, please visit the official PacketCache page:
https://www.netresec.com/?page=PacketCache

PCAP or it didn't happen!

Posted by Erik Hjelmvik on Wednesday, 28 September 2016 11:45:00 (UTC/GMT)

Tags: #PacketCache​ #PCAP​ #NSM​ #forensics​ #Windows​ #sniffer​ #memory​ #DFIR​

From 4SICS with ICS PCAP Files

4SICS is the the leading Industrial Control System (ICS) security conference in Europe, which brings in speakers and attendees from all around the world. I tought a one-day class on analyzing network traffic as part of the pre-conference training at 4SICS. In this class we analyzed PCAP files containing industrial protocols, such as Modbus/TCP and IEC-104. Unfortunately there aren't many capture files around that carry these protocols, so the ICS analysis part in my class wasn't as advanced as I wanted it to be.

I have been aware of this limited access to ICS traffic for some time now, which is why I decided to work with the 4SICS crew in order to set up a sniffer in the ICS lab at the 4SICS conference. This lab contained devices such as PLCs, RTUs, servers, industrial network equipment (switches, firewalls, etc), which were available for hands-on "testing" by 4SICS attendees.

The network TAP vendor Garland were Technology Partners at 4SICS, so I didn't even have to bring a network TAP to the lab. I just connected my sniffer machine and let it record for three days. Chris Sistrunk also joined the sniffing party later in the conference by connecting his SEL-3355, which runs SecurityOnion, to the network TAP.

The 350MB of network traffic that was captured during the 4SICS conference is now publicly available here:
https://www.netresec.com/?page=PCAP4SICS

Enjoy!

Posted by Erik Hjelmvik on Wednesday, 04 November 2015 15:45:00 (UTC/GMT)

Tags: #ICS​ #SCADA​ #PCAP​ #4SICS​ #IEC-104​ #Modbus​ #sniffer​ #PLC​