NETRESEC Network Security Blog
Unencrypted network traffic, destined for the Tor network, is sent between localhost TCP sockets on computers running Tor clients, such as the Tor Browser. In this blog post I show how anonymous Tor browsing can be visualized, by loading a PCAP file with localhost traffic into NetworkMiner. We call this technique TorPCAP.
Tor is a secure platform that enables users to browse the web anonymously. The Tor Project website describes the tool as:
“Tor is free software and an open network that helps you defend against traffic analysis”
It is also possible to host anonymous “onion services” on the Dark Web using Tor:
“Tor makes it possible for users to hide their locations while offering various kinds of services, such as web publishing or an instant messaging server. Using Tor "rendezvous points," other Tor users can connect to these onion services, formerly known as hidden services, each without knowing the other's network identity.”
Capturing Tor Traffic Before it gets Encrypted
Tor installations include a SOCKS proxy listening on TCP port 9150 on localhost (127.0.0.1). This local SOCKS proxy is used by the Tor Browser, which connects to the proxy in order to have its traffic encrypted and forwarded to the Tor network. This means that by sniffing traffic on localhost it’s actually possible to create a solid forensic trail of all traffic a PC sends to and from the Tor network.
You can use tcpdump to capture the localhost traffic on PCs running the Tails OS or Tor Browser in MacOS or Linux. If you’re running the Tor Browser in Windows, then we recommend using RawCap to sniff the localhost traffic (RawCap is a portable standalone tool that doesn’t need WinPcap or NDIS drivers to work).
In order to make sense of the captured traffic you need a tool that can parse the SOCKS protocol (RFC 1928). NetworkMiner includes a SOCKS parser since version 2.1, which can be used to extract and reassemble data going to and from the Tor network.
Demo: Analysing TorPCAP Network Traffic
A user, let’s call him “Eldon”, used Tor for some dark-web activity on November 30, 2018. Eldon was using the Tor Browser on a Windows PC and RawCap was used to capture the localhost network traffic from Eldon’s computer. A PCAP file with the captured packets from Eldon’s PC can be accessed here. Please feel free to open this capture file with NetworkMiner, in order to follow along in this analysis.
File : rawcap-localhost-tor.pcap
Size : 1.47 MB
SHA256 : 9134FA542B388498C2A58A2E1424FCD4AF466CE7117DBE9AAFD0A031CC8209B8
The “Files” tab in NetworkMiner contains a list of all files that have been reassembled from the analyzed PCAP file. This file listing reveals that Eldon used the “not Evil” search engine (hss3uro2hsxfogfq[.]onion) to search for “buy fake passports” in frame 1136.
The search result page from not Evil has been reassemled by NetworkMiner as “index.php.CB66877E.html”. By opening this HTML document in a browser we can see which search results Eldon got (no Internet connection is needed to open the reassembled html).
The “Browsers” tab in NetworkMiner Professional shows that Eldon followed the link for entry #2 in his search results (BUY FAKE PASSPORTS [...]), leading him to the “fakeimz[...].onion” website.
Eldon then proceeded to list the available passports (see the reassembled file “novelty_fake_id_samples.shtml” in frame 1837) and chose the UK passport (“pp-uk-open-big.jpg”).
As Eldon proceeded he got a price list for the fake passports offered at this site (“novelty_fake_id_pricing.shtml”), but we don’t see any evidence of him actually completing a purchase of a fake UK passport.
If we go back to the Images tab in NetworkMiner, and scroll a bit further down we see a picture of a gun. Let’s see where it comes from.
It turns out Eldon also searched for “buy guns for bitcoin UK”. You can list all search engine queries by looking for entries in the “Parameters” tab with parameter name “q”. This technique is applicable for the “not Evil” search engine as well as most clearnet search engines, like Google, Bing, Yahoo! and DuckDuckGo (disregarding the fact that they use TLS).
The Browsers tab shows us that Eldon clicked on a link to the “UK Guns and Ammo Store” (tuu66[...].onion).
This website has also been passively reassembled by NetworkMiner and can be opened offline in a browser (see “index.html”).
The Credentials tab in NetworkMiner shows the username and password used by Eldon to log into the website:
After logging in, Eldon puts two items in his shopping cart (see “cart.php.html”), but gets a message saying “Not enough balance for this order” when clicking the “Continue to Checkout” link. It seems Eldon’s account at the dark-web weapons store doesn’t have any Bitcoins (see “wallet.php.html”)
Side Note - Web Trackers and Tor
It is considered bad practice to use clear-net tracking services, like Google Analytics, to track users visiting an onion service. However, we noticed that the fake passports website uses a Google Analytics script with tracking ID “UA-19359933-1”.
Googling this ID led us to this very similar website:
Posted by Leon Kowalski on Wednesday, 12 December 2018 09:33:00 (UTC/GMT)
This blog post describes how to dump a packet capture (pcap file) on a remote computer, which runs the PacketCache service, and retrieve that pcap file using only PowerShell.
PacketCache is a free Windows service that continously sniffs network traffic on all interfaces (Ethernet, WiFi, 3G, LTE etc) and maintains a cache of the most recent traffic in RAM. This enables incident responders to read PCAP data out of a PC's PacketCache, for example when an IDS or anti-virus alerts on something potentially malicious. Unfortunately, there is no central management tool for PacketCache, which means that the PCAP data has to be dumped locally at the PC that triggered the IDS or AV alert.
There are a few workarounds "hacks" available to solve this problem, but the most elegant solution is to leverage PowerShell Remoting / WinRM in order to trigger a remote PacketCache instance to create a PCAP file and then copy the PCAP file through the same PowerShell session. To make things even simpler we've created a PowerShell script that can be used to download a PCAP file from any machine running PacketCache. Okay, maybe not *any* machine, the script only works on PCs that you have admin credentails for. Nevertheless, here's how you run the script from a PowerShell prompt:
The ReadRemotePacketCache.ps1 script can be downloaded from the PacketCache product page.
Configuring Hosts for PowerShell Remoting
If you have not previously set up your environment for PowerShell remoting, then you will need to follow these steps before invoking the "ReadRemotePacketCache.ps1" script as above.
On the remote PC, start PowerShell as administrator and enable PowerShell remoting with the "Enable-PSRemoting" command as shown here:
Configuring TrustedHosts for Workgroups
You will also need to set up a trust relationship between the local and remote host. If the remote PC is member of an Active Directory domain, then this trust is already in place. However, if you're in a workgroup or the computers are not in the same domain, then you will need to set the TrustedHosts item like this on both the local PC and the remote PC:
Note: if you need to dump PacketCache data from several remote hosts, then you can replace the IP/hostname with '*' to trust any PC or supply a comma separated list of individual hostnames or IPs to trust.
If you've configured TrustedHosts correctly, then you should be able to run the "ReadRemotePacketCache.ps1" script as shown previously. However, if the remote PC isn't in TrustedHosts, then you'll most likely get an error message like this:
Automating Remote Artifact Collection
With PowerShell remoting in place you're not limited to just dumping packets from a remote PacketCache service, you can also dump the RAM or copy individual files from the remote computer. This comes in handy in order to implement an automated evidence/artifact collection, for example when a high-severity alert is received by your SIEM.
There are frameworks in place that can help with aquisition of memory and files, such as Matthew Green's Invoke-LiveResponse tool, which can dump memory with WinPMEM and leverage PowerForensics to enable remote raw disk access. Some organizations even start sniffing packets at events like this, but this will only capture the traffic from after a potential compromize. This is where PacketCache comes in, since it can allow you to retrieve packets ranging back as far as a couple of days before the alert.
It is recommended to use unique passwords for each local account with administrator rights. This practice is extra important if you plan to log into a potentially compromized host using administrator credentails, as described in this blog post. You might also want to lock down the local admin accounts even further in order to minimize the consequences of the admin credentials falling into the wrong hands. See Microsoft's articles on "Local Accounts" and "Attractive Accounts for Credential Theft" for more recommendations regarding how to secure local admin accounts.
PacketCache is Free
PacketCache is free to use, even commercially. It is released under a Creative Commons Attribution-NoDerivatives 4.0 International License, which means that you can copy and redistribute PacketCache in any medium or format for any purpose. You can download PacketCache here:
The PowerShell script presented in this blog post is also shared under the same CC license and can be downloaded from the PacketCache product page.
I'd like to thank Dick Svensson for suggesting the use of PowerShell Remoting to read PacketCache data remotely!
Posted by Erik Hjelmvik on Wednesday, 14 November 2018 08:00:00 (UTC/GMT)
One of the highlights at this year’s SEC-T conference in Stockholm was Steve Miller’s talk titled "Reversing the TriStation Network Protocol". In this talk Steve covered his quest to better understand the TRITON malware, which had been used in a targeted attack of an industrial control system (ICS). Steve didn’t disclose the type or location of the plant, saying “Don’t ask me who it was, ‘cause I can’t say” when the Q&A started. However, an article in the Wall Street Journal points out that it was a petrochemical plant in Saudi Arabia that had been hacked.
Targeting Safety Instrumented System
The TRITON malware (also called TRISIS) was used to target a safety instrumented system (SIS) from Schneider Electric called Triconex. A SIS is typically not used to control the process of a plant, but rather to detect abnormal operating conditions and safely shut down the industrial process if needed.
I could elaborate a lot regarding the consequences of attacking the SIS, but the good guys from Dragos have already done a great job explaining this in their “TRISIS Malware” report.
Reverse Engineering the ICS Protocol
The communication protocol used by the Triconex controllers is called TriStation, which is a proprietary protocol. This means that there were no publicly available specifications available for the protocol at that time. There was also no Wireshark dissector that could parse TriStation traffic. Nevertheless, Steve’s initial reaction to this was “Awesome, undocumented things are my favorite things!”
Unfortunately Steve wasn’t able to get hold of a single PCAP file with the TriStation network protocol, which made it really difficult to reverse engineer the protocol implementation in the TRITON malware. The only piece of actual TriStation network traffic he was able to get hold of was a hex dump of a TriStation packet in an academic paper.
Armed with only the hexdump and Wireshark’s text2pcap Steve managed to piece together an actual PCAP file containing a single frame with a TriStation packet inside.
As you can see in the image above, Wireshark doesn’t decode any of the application layer data coming from TCP port 1502 (which TriStation uses). He therefore implemented a Wireshark Lua dissector for the TriStation protocol. And some time later the people from Nozomi Networks even implemented a proper Wireshark dissector for the TriStation protocol.
BSI’s ICS-SEC team have now also created Snort IDS rules specifically for the TriStation protocol. These IDS rules trigger on events like:
- Packets sent to the controller from an unauthorized host
- Malicious commands used by the TRITON malware to read and write to the RAM of the SIS controller as well as to execute code
The Importance of Sniffing ICS Traffic
I’ve been trying to convince asset owners, who use ICS in their power plants, factories, water treatment facilities etc, to start capturing the network traffic and storing it as PCAP files for many years now. However, asset owners sometimes try to argue that there is no point in capturing their traffic since it is using a proprietary protocol. Even Ralph Langner has opposed to the idea of capturing ICS network traffic in a blog post, which I have criticized. So, how difficult is it to write a parser for a proprietary protocol?
I have personally implemented support for over 30 application layer protocols in NetworkMiner, but unlike Steve I’ve always had access to at least one PCAP file and some form of documentation of the protocol. However, I’ve found that many real-world protocol implementations don’t follow specifications properly. In these cases I’ve found that having access to PCAP files with real-world network traffic is more important than having a full protocol specification.
Even complex proprietary protocols like the old proprietary Skype protocol has been reverse engineered, so with access to network traffic of a protocol combined with a binary that uses this protocol I’d say that pretty much any network protocol can be reverse engineered.
Steve’s SEC-T talk also proves that ICS protocols are no different, since they too can be reverse engineered without having a protocol specification or RFC.
Capturing network traffic in ICS networks is never wrong. There might not be parsers available today for all the protocols you’re using. But once a parser or IDS signature becomes available for the protocol you’re using, you can simply use that to analyze previously captured network traffic from your ICS network. Also, in the wake of an incident you might actually end up writing a parser (as in the TRITON case) or a custom IDS rule, in which case having historical network traffic from your plant in invaluable!
For more information on this topic I’d suggest reading my blog post titled “Monitor those Control System Networks!” from 2011, which still is highly relevant.
I’m also happy to announce that two PCAP files containing TriStation network traffic have been linked from our list of publicly accessible PCAP files today (see the “SCADA/ICS Network Captures” section).
And remember: PCAP or it didn’t happen!
Posted by Erik Hjelmvik on Friday, 21 September 2018 14:20:00 (UTC/GMT)
NetworkMiner 2.3.2 was released this morning, and there was much rejoicing!
Image: U.S. Navy photo by Stuart Phillips (source) Data Exfiltration Malware dataset loaded.
We’d like to thank Carlos Kasprzykowski for notifying us about the VoIP bug, which caused lots of files to be written to the %TEMP% directory when there were more than 50 simultaneous SIP+RTP calls. We also wanna thank Josh Wilczek for reporting a bug in the “User Defined Port-to-Protocol Mappings” in NetworkMiner Professional’s Settings window, which also has been fixed in the 2.3.2 release.
Upgrading to Version 2.3.2
Users who have purchased a license for NetworkMiner Professional 2.x can download a free update to version 2.3.2 from our customer portal. Those who instead prefer to use the free and open source version can grab the latest version of NetworkMiner from the official NetworkMiner page.
⛏ FOR GREAT JUSTICE! ⛏
Posted by Erik Hjelmvik on Monday, 27 August 2018 09:23:00 (UTC/GMT)
This short video demonstrates how you can search through PCAP files with regular expressions (regex) using CapLoader and how this can be leveraged in order to improve IDS signatures.
The EmergingThreats snort/suricata rule mentioned in the video is SID 2014411 “ET TROJAN Fareit/Pony Downloader Checkin 2”.
The header accept-encoding header with quality factor 0 used by the Pony malware is:
And here is the regular expression used to search for that exact header:
After recording the video I noticed that the leaked source code for Pony 2.0 actually contains this accept-encoding header as a
hard-coded string. Have a look in the
redirect.php file, where they set
Wanna learn more about the intended use of quality factors in HTTP accept headers?
Then have a look at
section 14.1 of RFC 2616section 5.3.4 of RFC 7231, which defines how to use qvalues (i.e. quality factors) in the Accept-Encoding header.
I submitted a snort/suricata signature to the Emerging-Sigs mailinglist after publishing this blog post, which resulted in the Emerging Threats signature 2014411 being updated on that same day to include:content:"|0d 0a|Accept-Encoding|3a 20|identity,|20 2a 3b|q=0|0d 0a|"; http_header;
Thank you @EmergingThreats for the fast turnaround!
Posted by Erik Hjelmvik on Wednesday, 04 July 2018 07:39:00 (UTC/GMT)
We are happy to announce the release of CapLoader 1.7!
Here’s an overview of what’s new in this release:
- Regular expression searching
- Lookup of IP addresses using online services
- Lookup of domain names using online services
- Improved protocol fingerprinting speed and precision
- Support for GRE, IGMP and ICMPv6 flows
- More precise period estimation of “periodic services”
Regular Expressions Search
CapLoader’s “Find Keyword” window has been extended with an option to search flows using regular expressions (regex) as an alternative to searching for strings or byte sequences. With help of the powerful regex syntax built into .NET this new search option enables very flexible searching.
Image: Searching for Alfa Ransomware flows using regex
The Find Keyword window can be opened by clicking Edit > Find Keyword, or by pressing
You can learn more about regex searching with CapLoader in our short video called "Detecting the Pony Trojan with RegEx using CapLoader".
OSINT Lookups of IP Addresses and Domains
We added support for querying online services for IPs and domain names to the latest release of NetworkMiner, now it’s time to add this very handy feature to CapLoader as well.
Right-clicking a Flow, Service or Host in CapLoader brings up a context menu with links to various online resources that might have more details regarding the clicked IP address or domain name.
The services available for IP address OSINT lookup include:
APNIC Whois, Censys, Cymon, ExoneraTor, Google Public DNS, GreenSnow.co, Hurricane Electric, IBM X-Force, Internet Storm Center, mnemonic Passive DNS, PacketTotal, SecurityTrails, Shodan, ThreatCrowd, ThreatMiner, UrlQuery and VirusTotal.
The domain name lookup menu contains a similar set of providers:
Cymon, Google Public DNS, Google Safe Browsing, Hybrid Analysis, IBM X-Force Exchange, mnemonic Passive DNS, MXToolBox, MyWOT, Norton Safe Web, PacketTotal, SecurityTrails, ThreatCrowd, ThreatMiner, URL Void, UrlQuery, VirusTotal, Website Informer, Webutation and Whoisology.
The dynamic protocol detection (or Port Independent Protocol Detection, aka “PIPI”) in CapLoader has been improved to support even more protocols than before. We have also fine-tuned the protocol identification algorithm to be both faster and more accurate.
Image: Traffic to TCP 8777 identified as SSL (PCAP file from Stratosphere IPS)
Updating to the Latest Release
Users who have previously purchased a license for CapLoader can download a free update to version 1.7 from our customer portal. All others can download a free 30 day trial from the CapLoader product page (no registration required).
We’d like to thank Michael Nilsson for suggesting the IP and domain name lookup feature and Tohar Braun for suggesting RegEx search support. We’d also like to thank Ralf Alvarsson and Jarmo Lahtiranta for reporting bugs that have been resolved in this release.
Posted by Erik Hjelmvik on Tuesday, 03 July 2018 11:37:00 (UTC/GMT)