Archive for the ‘OTX’ tag

Control code usernames in telnet honeypot  

Posted at 9:19 am in Uncategorized

By running a Cowrie honeypot, I’m gathering interesting information about various kinds of exploits, vulnerabilities, and botnets. Upon a discovery of a new Linux-based vulnerability – often targeting network routers, IoT devices, and lately many IP camera products – the botnets will usually come in waves, testing the new exploits.

The honeypot logs everything the intruders to. In addition to extracting and submitting useful indicators to threat intelligence resources like VirusTotal and AlienVault’s Open Threat Exchange, I’m processing the logs in an Elastic stack for graphing and trending. As shown below, there’s a section of the Kibana dashboard that details activity by time range and geolocation, and I’m also listing the top 10 usernames and passwords used by intruders trying to gain access.

Parts of my Cowrie dashboard in Kibana

Parts of my Cowrie dashboard in Kibana

This morning I briefly checked the top 10 usernames tag cloud when something unusual caught my eye.

KIbana username tag cloud

It wasn’t the UTF rectangle added to the “shell” and the “enable” user names, these are really shell\u0000, enable\u0000, sh\u0000 and are appearing quite frequently nowadays. What caught my eye was this tiny, two-character username, looking like an upside-down version of the astrological sign for Leo and a zigzag arrow.

Weird username from tag cloud

Upon closer inspection, the username is actually \u0014\t\t\u0012 – “Device Control 4”, two TABs, and “Device Control 2”.

One of the passwords used with this username was \u0002\u0003\u0000\u0007\u0013 – visualized in Kibana as follows:

Other passwords from the same IPs also include different control codes, beautifully visualized by Kibana as shown below:

From the Cowrie logs, the first occurrences in my honeynet were 2017-12-16. Exactly what kind of vulnerability these control codes are targeting is not known to me yet, but I am sure we will find out over the next few days.

Written by bjorn on December 21st, 2017

Tagged with , , , , , , , ,

Threat intelligence: OTX, Bro, SiLK, BIND RPZ, OSSEC  

Posted at 8:15 am in Uncategorized

Building a toolbox around threat intelligence can be done with freely available tools. Shared information about malicious behaviour allows you to detect and sometimes prevent activity from – and to – Internet resources that could compromise your systems’ security.

I’ve already described how to use lists of malicious domain names in a BIND RPZ (Response Policy Zone). Adding an information feed like AlienVault OTX (Open Threat Exchange) to the mix further extends the awareness and detection capabilities.

AlienVault is probably most known for their SIEM (Security Information and Event Management) named Unified Security Management™, with a scaled-down open source version named Open Source Security Information and Event Management (OSSIM). They also provide a platform for sharing threat intelligence, namely Open Threat Exchange (OTX). OTX is based on registered users sharing security information, for instance domains and hostnames involved in phishing scams, IP addresses performing brute force SSH login attempts, etc. The information is divided into so-called pulses, each pulse a set of information items considered part of the same malicious activity. For example, a pulse can contain URLs to a site spreading drive-by malware, the IP addresses of their C&C, along with hashes of the files. By selecting which pulses and/or users to subscribe to, the registered information in each pulse will be available through a feed from their API.

Carefully reviewing which users/pulses to subscribe to – there’s always a risk of false positives – I’m now regularly receiving an updated feed. This feed is parsed and currently split into two files: One RPZ file containing hostnames and domains for use with BIND, and one file containing IP addresses for use with SiLK.

As explained in an earlier post, OSSEC will let me know if someone (or something) makes DNS requests for a domain or hostname registered as malicious. Extending this to include the DNS records obtained from OTX was simply a matter of defining a new RPZ in BIND. Depending on how this is used (block? redirect? alert?), a whitelist should be in place to prevent accidental blocking of known good domains. One pulse describes all the Internet resources a client infected by a certain exploit will contact, including some certificate authorities which are not necessarily considered evil.

The file with IP addresses can be used directly with a firewall, by logging or even blocking or throttling traffic to/from the IP addresses in question. For rear-view mirror analysis it can be used with SiLK, to find out if there has been any network traffic to or from any of these addresses. To do this, you will first have to create an IP set with the command rwsetbuild:

# rwsetbuild /some/path/ip-otx.txt /some/path/ip-otx.set

 

Now we can use this set file in our queries. For this query I’ve manually selected just a few inbound matches:

# rwfilter --proto=0-255 --start-date=2016/01/01 \
  --sipset=/some/path/ip-otx.set --type=all \
  --pass=stdout | rwcut -f 1-5
            sIP|            dIP|sPort|dPort|pro|
   185.94.111.1|  my.ip.network|60264|   53| 17|
   216.243.31.2|  my.ip.network|33091|   80|  6|
   71.6.135.131|  my.ip.network|63604|  993|  6|
   71.6.135.131|  my.ip.network|60633|  993|  6|
   71.6.135.131|  my.ip.network|60888|  993|  6|
   71.6.135.131|  my.ip.network|32985|  993|  6|
   71.6.135.131|  my.ip.network|33060|  993|  6|
   71.6.135.131|  my.ip.network|33089|  993|  6|
   71.6.135.131|  my.ip.network|33103|  993|  6|
   71.6.135.131|  my.ip.network|33165|  993|  6|
   71.6.135.131|  my.ip.network|33185|  993|  6|
   71.6.135.131|  my.ip.network|33614|  993|  6|
   71.6.135.131|  my.ip.network|33750|  993|  6|
   71.6.135.131|  my.ip.network|60330|  993|  6|
  185.130.5.224|  my.ip.network|60000|   80|  6|
  185.130.5.224|  my.ip.network|60000|   80|  6|
  198.20.99.130|  my.ip.network|    0|    0|  1|
  185.130.5.201|  my.ip.network|43176|   53| 17|
  129.82.138.44|  my.ip.network|    0|    0|  1|
  185.130.5.224|  my.ip.network|60000|   80|  6|
  185.130.5.224|  my.ip.network|60000|   80|  6|

 

When you need more details about the listed address or other indicators, OTX provides a search form to find the pulse(s) in which the indicator was registered.

OTX can be used with Bro as well, and there are at least two Bro scripts for updating the feeds from the OTX API. The one that works for me is https://github.com/hosom/bro-otx. The script will make Bro register activity that matches indicators from an OTX pulse.

Sample log entries, modified for readability:

my.ip.network 59541 some.dns.ip    53 - - - union83939k.wordpress.com
                                            Intel::DOMAIN DNS::IN_REQUEST
my.ip.network 40453 54.183.130.144 80 - - - ow.ly
                                            Intel::DOMAIN HTTP::IN_HOST_HEADER
74.82.47.54   47235 my.ip.network  80 - - - 74.82.47.54
                                            Intel::ADDRConn::IN_ORIG

 

This article mentions just a few components that can be combined. Obviously there’s a lot of possibilities for integrating and interfacing between different systems. There are several companies that provide threat intelligence feeds, some for free and some for paying customers. Depending on the product(s), a SIEM would be able to combine and correlate the different kinds of threat intelligence to detected events.

Written by bjorn on March 9th, 2016

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