With the advent of staff being more and more mobile with work activities, they are often not in the office. This remote teleworking has been a growing trend for many years and can mean that employee systems are not on the corporate network ever or very infrequently. If the systems are not on the corporate network, then the audit logs and other activity from their laptops cannot always be collected in near real time as there is no connection to the internal SIEM system that is typically on the corporate network. The corporate SIEM systems need to be protected and rarely on open networks as they contain sensitive information and need to be protected from tampering and viewing from unauthorized parties. This can leave the end point systems exposed to unauthorized activity from the staff member doing something they should not be doing, or to being hacked from an external party while on some other open network like a Starbucks, a cafe, a hotel or an airport’s wireless network for example. If the system gets compromised, then no log or alert information can be sent to the corporate SIEM and the security teams won’t know that one of their employees was just hacked. In general, most connections would require the employee to VPN when remote or go into an office location to connect to the LAN so the logs can be sent to the corporate SIEM. But by then the system may already be compromised so it could spread the malware on the corporate network and result in a larger scale incident. Many attacks can go unnoticed after a seemingly innocuous event such as not patching the system, a user clicked on a malicious link and malware was installed, a remote hacker exploits some weakness in the systems settings or via a new day zero vulnerability. Some attacks may try and hide on users’ systems until the user connects back to the corporate network but there will still be subtle bits of activity that can be detected and reported on with software installs and process execution.

So how can Snare help with this problem?

We have the capability to collect the logs from the employee’s system in near real time over the internet, all securely over TLS using a mutual authentication key to our Snare Collector/Reflector technology. The system can be open to the internet and only allow authorized connections from the Snare agents to the Snare Collector/Reflector. Any system that does not have the relevant authorization keys won’t be allowed to connect. Along with TLS certificate strict validation the destination connection can be trusted and securely send the log data to the central SIEM. The connection works much like a VPN does for the traditional laptop to corporate network when a user is remote, but it limited only to the Snare Agent and the Snare Collector/Reflector for sending log data. This then allows all remote workers systems to have near real time monitoring and collect the audit logs whenever they are on the Internet such as in a cafe, hotel, airport or a Starbucks, which are all common areas they can be exposed from a remote exploitation attack, so this ability helps with early incident detection and data breaches of the users endpoint system before it can spread to other users and the corporate network. The technology can be deployed on the corporate network or in the cloud and reflected around to other parts of the network and multiple SIEM systems as needed to facilitate early warnings and reporting for the security team and any SOC an organisation has in place. The time to detection of a breach is always critical to containment and minimizing any business impact. That’s why collecting the data in near real time is always important to minimize the impact to the business.

As many know, the US Cyber Command issued a recent emergency directive for DNS Infrastructure Tampering.

While much of the directive relates to validating organisational DNS, password and MFA settings, one key aspect of the directive discusses the monitoring and management of authorised and unauthorised changes to the DNS environment. In order to meet this requirement, adequate logging should be in place to monitor changes to the DNS settings, and log data should include date/time information as well as information on who is making the changes. Snare can help meet this requirement in several ways.

The Snare enterprise agents can track all access and modification to the DNS settings on Windows and Unix systems.

The key aspects of the logs that can be collected are:

  • All user authentication activity. If the user logs into the system either from the local console, Active Directory, or via ssh on Unix then Snare can collect the relevant operating system audit events or kernel events to show that a specific user logged into the system. This data will include the source IP, authentication type, relevant success and failure of the attempt and the date and time stamp of the activity.
    • Microsoft has technical articles on how to configure your audit policy to generate the specific events both on legacy 2003 and newer 2008R2, 2012R2, 2016 and 2019 systems that support advanced audit policies.
    • All the events are quite detailed, and include:
      • Who made the changes,
      • What the changes were,
      • What zones were affected and obviously,
      • When these changes occurred.
  • The Microsoft custom event logs on Windows 2008R2, 2012R2, 2016 and 2019 also include DNS Server and DNS client eventlog categories. The Snare agent will collect these using the default objectives. The events collected show additional changes to the DNS records that can occur through either manual or dynamic updates associated with Active Directory DNS and zone files. A summary of the event types are:
    • 512, 513,514,515,516 – ZONE_OP – These can be part of major updates and changes to the zone files.
    • 519,520 DYNAMIC_UPDATE
    • 536 CACHE_OP
    • 537,540,541 Configuration – these events will be the areas of main concern with systems changes.
    • 556 SERVER_OP
    • 561 ZONE_OP
  • The Snare agent for windows will collect DNS Server logs as part of the default configuration.
  • As part of the installation process, the Windows agent can be told to manage the configuration of the Windows audit subsystem, to ensure that it generates the relevant administrative events.  Alternatively, the Snare for Windows agent can be configured to be subservient to manually configured local policy or group policy settings. It should be noted that unless the associated audit subsystem is appropriately configured, events may not be delivered to the Snare for Windows agent, for processing.
  • For Unix systems the the DNS files are usually flat text files.  The Snare Linux agent can use two aspects to monitor the files
    • File watches: The agent can be configured to watch for any and all changes to specific files related to DNS configuration settings, and will raise kernel audit events on access or modification, including details of who accessed/changed the file, and date/time information associated with the event. On Linux  systems, configuration files related to bind, dnsmasq or other DNS server tools may be monitored.
    • The default administrative Objectives for the Linux agent, track all user logins, administrative activity, an privileged commands. File watches are also configured for for changes to the /etc directory, which hosts system level configuration files for the operating system.
  • File Integrity Monitoring – The Snare Linux agent can also perform sha512 checksum operations on system configuration files, such as DNS configuration files, in order to watch for changes. This will track all new files, changes to files or deletion of files and directories being monitored. These events dont show who did the change but will track the actual changes and permission changes to files. The FIM monitoring can be run on a configurable schedule (eg: once per hour or once per day) depending on the level of granularity wanted.
  • Once the logs have been generated then its up to the SIEM and reporting systems to provide reports or alerts relating to the changes. Snare offers two complimentary method for this:
    • Snare Central – this can provide objective reports looking for the specific event IDs and produce a report in tabular format as well as graph and pie charts of the activity. These can be emailed out on any schedule needed to include the PDF report, CSV and text output as needed.
  • Snare Advanced Analytics – For this we can provide a a view of changes that occur in the system and update the dashboard in near real time as the logs are being collected.
  • As part of normal operations all changes should be validated as part of approved activity as per your normal operating procedures and anything that is not approved would be escalated as a incident for investigation.

If your organisation needs help in this area and you would like more information, please contact our friendly sales team at snaresales@prophecyinternational.com for a chat on how we can help your business achieve a more effective and efficient CISA DNS monitoring solution.

Steve Challans

Chief Information Security Officer

https://www.snaresolutions.com