Getting DNS Client Cached Entries with CIM/WMI

in , , ,

What is DNS Cache

The DNS cache maintains a database of recent DNS resolution in memory. This allows for faster resolution of hosts that have been queried in the recent past. To keep this cache fresh and reduce the chance of stale records the time of items in the cache is of 1 day on Windows clients. 

The DNS Client service in Windows is the one that manages the cache on a system, This time Window can be modified via the registry in the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters where the MaxCacheTtl property controls the time in the cache in seconds and the MaxNegativeCacheTtl property controls the time a failed response is cached.  

Why is it Important

For an attacker, it means primarily situational awareness. It allows him to know what other systems this host has accessed and the IP address of the host. This may allow identifying security platforms by the FQDNs used as well as business process systems, both internal or in the cloud. On an important note for the attacker is that if his implant/agent on the system does not include its own resolution capability it has an IOC present on the system that can be used to track its command and control infrastructure. 

For a defender, the ability to know what hosts a system may have connected to in the last 24 hours. This will permit a defender to query across his environment for hosts that are communicating or have communicated with a specific host if DNS resolution was part of the process and if the attacker is not using its own resolution method. If the attacker is “Living off the Land” and using OS tools it will still leave the femoral trace on the system until the cached entry TTL (Time to Live) expires.

MSFT_DNSClientCache class

In Windows 8/2012 Microsoft added the MSFT_DNSClientCache class into the CIM object database in Windows. The class is under the new namespace that was also added to Root\StandardCimv2 and the resources are provided as part of the DnsClientCim.dll. This allows us to query for instances of the class and get all entries for the DNS Cache database. 

Read More

Being Grateful at Heilderburg

Recently while in the bar of the Crown Plaza in Heidelberg for the Troopers conference I became aware of the number of how grateful I should be for what I have in this industry. For what I’m grateful for is not technical or recognition but of the group of people in the industry, I have the honor to call friends.

I would like to share some of them in this blog post. While coming back from dinner at Heidelberg JD also known as @SadProcessor send me a DM that several of our friends are at the hotel bar and even so I don't drink I should come down and hang out. I was jet lag but had not seen many of them in months so I said to myself “Why not” so I went down.

Read More

Operating Offensively Against Sysmon

in , ,

Sysmon is a tool written by Mark Russinovich that I have covered in multiple blog post and even wrote a PowerShell module called Posh-Sysmon to help with the generation of configuration files for it. Its main purpose is for the tracking of potentially malicious activity on individual hosts and it is based on the same technology as Procmon. It differs from other Sysinternals tools in that Sysmon is actually installed on the host and saves its information in to the Windows Eventlog so it is easier to be able to collect the information with the use of SIEM (Security Information and Event Management) tools. 

 Sysmon has the capability to log information for:

  • Process Creation and Termination

  • Process changing a file creation time.

  • Network Connection

  • Driver Load

  • Image Load

  • CreateRemoteThread

  • Raw Access Read of a file

  • A process opens another process memory

  • File Creation

  • Registry Events

  • Pipe Events

  • WMI Permanent Events 

Read More

Rebuilding My Playbook .. Knowledge Base

I find myself in the situation where I lost my personal playbook by user error. I accidentally deleted the VM where I ran xWiki where it was kept and did not realized the mistake until days later. Even if painful to rebuild it is a good opportunity to think on how to better organize it and put it in a more flexible format.  

I Initially called my collection of techniques as playbook, but in reality they where not one. It was simply a collection from which I wold pull depending on the situation and as reference when writing presentations, blog posts and reports. To me a playbook is a collections of plays, each play composing of multiple steps that would vary depending environment and purpose. So the term playbook really did not fit. As I rebuild now I have decided to call it a Knowledge Base. By calling it a Knowledge Base this gives me the advantage to properly later build a real playbook where I can cover small samples of multiple steps and tools together that I can pull in to planning in to the different stages using the PACE (stands for Primary Alternate Contingency Emergency) principal where it makes sense. 

If you have ever taken the OSCP Exam from OffensiveSecurity you have learned the importance of having a knowledge base with the right information. You also learn as you progress through the material and labs to build and hopefully not fail on the first try.

Read More

Operational Look at Sysinternals Sysmon 6.20 Update

Sysmon has been a game changer for many organizations allowing their teams to fine tune their detection of malicious activity when combined with tools that aggregate and correlate events.  

A new version of Symon was recently released. Version 6.20 fixes bugs and adds new features. Some the of the note worthy changes for me are:

  • Enhancements in WMI Logging. 
  • Ability to change driver name. 
  • Ability to change service name and service executable name.
Read More