Tag Archives: CIS Benchmarks

BASH cli Scripts for CIS Benchmarks for Azure

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Like the catchy title?

Anyway – here’s a few cheeky scripts for testing a handful (for now) of aspects of the CIS Benchmarks 2.0 for Azure. You have to populate the subscriptions.txt file for each.

Go To Github

Each subdirectory under the repository root corrresponds with a CIS Benchmark reference for Azure 2.0:

  • 1.4, 1.5 – Review Guest Users – script list the Guest users configured in Entra
  • 1.23 – Ensure That No Custom Subscription Administrator Roles Exist
  • 3.1 – Ensure that ‘Secure transfer required’ is set to ‘Enabled’ [Storage Accounts]
  • 3.2 – Ensure that ‘Enable Infrastructure Encryption’ for Each Storage Account in Azure Storage is Set to ‘enabled’
  • 3.7 – Ensure that ‘Public access level’ is disabled for storage accounts with blob containers
  • 3.10 – Ensure Private Endpoints are used to access Storage Accounts
  • 3.11 – Ensure Soft Delete is Enabled for Azure Containers and Blob Storage
  • 3.12 – Ensure Storage for Critical Data are Encrypted with Customer Managed Keys
  • 3.15 – Ensure the “Minimum TLS version” for storage accounts is set to “Version 1.2”
  • 5.1.3 – Ensure the Storage Container Storing the Activity Logs is not Publicly Accessible
  • 5.1.6 – Ensure that Network Security Group Flow logs are captured and sent to Log Analytics
  • 6.5 – Ensure that Network Security Group Flow Log retention period is ‘greater than 90 days’
  • 6.7 – Ensure that Public IP addresses are Evaluated on a Periodic Basis (lists the addresses)
  • 7.4 – Ensure that ‘Unattached disks’ are encrypted with ‘Customer Managed Key’ (CMK) (lists unattached disks)
  • 8.2 – Ensure that the Expiration Date is set for all Keys in Non-RBAC Key Vaults (usually all key vaults will be RBAC enabled, making this control non-applicable. One script lists the RBAC and non-RBAC Key Vaults, then there’s an untested script for listing the non-expiring keys)
  • 8.3 – Ensure that the Expiration Date is set for all Secrets in RBAC Key Vaults. The script is untested because of a lack of access to a test key vault(s).
  • 8.4 – Ensure that the Expiration Date is set for all Secrets in Non-RBAC Key Vaults (usually all key vaults will be RBAC enabled, making this control non-applicable. One script lists the RBAC and non-RBAC Key Vaults, then there’s an untested script for listing the non-expiring secrets)
  • 10.1 – Ensure that Resource Locks are set for Mission-Critical Azure Resources

Some of the cli scripts offered by CIS in their Azure benchmark don’t work – Azure changes faster than the benchmarks after all. The above were tried and tested in a real live environment (no, those are not the subscription IDs listed in the subscriptions.txt files!!). 5.1.6 is an example. The ‘nsg’ parameter was made obsolete. Technically the script will run with a warning if the ‘nsg’ parameter is used, but anyway I have done as suggested and used the ‘–location and –name combination’ in the az network watcher command instead.

There will be more to come! Watch this space.

AuditpolCIS – Automating Windows SIEM CIS Benchmarks Testing

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In the previous post on the subject of Windows SIEM, we covered the CIS benchmarks for Windows Auditing Policy in a spreadsheet, which was provided freely (really, actually free).

This week we introduce a python open source tool we have developed, to automate the CIS Benchmark testing.

Download AuditpolCIS

Meeting Regulatory / Compliance / Audit Requirements

The automated assessment results from AuditpolCIS, as it’s based on CIS Benchmarks, helps in the support of meeting audit requirements for a number of programs, not least PCI-DSS:

  • Audit account logon events: Helps in monitoring and logging all attempts to authenticate user credentials (PCI-DSS Requirement 10.2.4).
  • Audit object access: Monitors access to objects like files, folders, and registry keys that store cardholder data (PCI-DSS Requirement 10.2.1).
  • Audit privilege use: Logs any event where a user exercises a user right or privilege (PCI-DSS Requirement 10.2.2).
  • Local log files sizes and retention policies are useful in assessing compliance with e.g. 5.3.4 and 10.5.1 requirements (PCI-DSS 4). There should be a block of text after the audit policy results.

Usage / Setup

First you will to set up a Python Virtual Environment. Ensure that you have Python installed on your system (Python 3.10 was used in development). If not, download and install Python from the official website: https://www.python.org/downloads/

Open a Command Prompt or terminal window and navigate to the folder where you extracted the AuditpolCIS project.

Run the following command to create a new virtual environment: 

python -m venv venv

Activate the virtual environment by running:

For Windows:

venv\Scripts\activate

For macOS/Linux:

source venv/bin/activate

Install the required Python packages from the requirements.txt file by running:

pip install -r requirements.txt

You will need a .env file in your project root. The contents relate to the target you wish to test:

HOSTNAME='<Windows box IP address or host name>'
USERNAME='<Windows user account name>'
PASSWORD='<account password>'

Make sure to assign the right ownership and permission on .env. Usually the permissions will be 600.

Once the virtualenv is enabled, you can run the code:

./auditpolcis.py


Feel free to branch or submit a PR.

Additional Points

The CIS benchmarks are based on Windows 2019 Server but they apply to other target varients on a Windows theme. I know none of you will have EOL Windows versions. <Sarcasm engaged>I mean in 22 years of consulting, i’ve never seen any out-of-support warez in critical business usage</Sarcasm engaged>.

Powershell is not required on the target but use of Powershell is also not a crime. Yes, that was a security person who said that.

Sustainability / Use of Regex

I had to use some fairly snazzy regex to pull out Categories (category_pattern = r'^(\w+.*?)(\r)?$') and Subcategories (subcategory_pattern = r'^( {2})([^ ]+.*?)(?=\s{3,})(.*\S)') from the auditpol command output. I did look at more sustainable ways of achieving the same goal, although admittedly i didn’t spend much time doing that. One thing has been clear for a long time with Windows – don’t go looking for registry keys because that can be very painful. Not only is documentation for a key location somewhat thin and erroneous, the key loation also often changes across Windows versions. ChatGPT‘s lack of knowledge of Windows reg keys bears testimony to the previous comments.

So there are two sources of Subcategory names – there is cis-benchmarks.yaml and there is the output of the auditpol /get /category:* command. If there are entries in the YAML file which are not in the auditpol output, they are flagged in the script output, and the same is true vice versa. So if you make spelling mistakes in the excel sheet or YAML file, it will be flagged. It can also happen that auditpol output subcategories do not reflect the CIS Benchmarks subcategories, perhaps with different Windows versions as targets. Any of these categories will be flagged by the script and listed below the pass/fail results.

If you want to change the verdicts or [Sub]Category names, you are of course free to do so. You can edit the cis-benchmarks.yaml file, or edit the included spreadsheet, followed by running the included genyaml.py.

Connection Method

The scripts works over SSH because other types of connection are a pain in the derriere and require you to radically increase your attack surface area, but if there’s a request for e.g. WinRM, please do let me know, or send out a Pull Request. Follow this link for more information about enabling the built-in SSH for Windows.

I know use of AutoAddPolicy with Paramiko in Python is not good form, but also assume that as an admin in the position of someone who performs daily tasks using administrative rights, that you know your hosts. Sometimes security people do get in the way of progress, when there’s low risk issues afoot. Use of RejectPolicy instead of auto-add would be one such case.

Tests Rationalisation

Some of the tests included are not a CIS Benchmark (out of 59 tests, 32 are CIS Benchmarks, whereas 27 are not). It’s not clear why the subcategories were omitted by CIS but anyway – in these cases we have made an assessment based on logging events volume for this subcategory, versus the security value of the subcategory. Most of these are just noise, and in many cases, very high volume noise, so we have advised “No Auditing”.

Customising Test Criteria

The testing template is formed of the YAML file cis-benchmarks.yaml. If you prefer to make changes to the testing template with Excel, the sheet is CIS-Audit-Reqs-Windows2019Server.xlsx in the code root. You can then use the python script genyaml.py to generate a new YAML file (you will need to use the right virtualenv, see above for usage instructions).

Windows SIEM – Optimizing Events Volume with CIS Benchmarks and AuditpolCIS

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In our 2021 blog post, we focused on identifying quick wins for optimizing Windows Events, and provided a free spreadsheet (really free, not even a regwall) that indicated Windows Events that could be safely ignored, some of which cost lots for SIEM engines to ingest. This post takes a broader Windows Audit Policy view, and offers another free resource – this time taking a broader look in the context of comparing your setup for Windows Audit Policy, and the venerable CIS Benchmark for Windows 2019 Server.

If there’s sufficient interest i’ll follow up with a development effort for a Python tool (also freely available, on Github) that connects to your Windows server and performs the CIS Benchmark assessment as indicated in the spreadsheet.

SIEM Nightmares

Based on many first hand observations and second hand accounts, it’s not a stretch to say that many organisations are suffering from SIEM configuration issues, for which the result is a low signal-to-noise ratio. Your SIEM is ingesting lots of events, many of which are not at all helpful, and with most vendors charging by volume, it gets expensive. At the same time, the false negative problem is all too common. Forensics investigations reveal all too often that there are no events recorded by the expensive SIEM, that even closely relate to the incident. I hope you are never in this scenario. The short-term impact is never good.

Taking SIEM as a capability, if one is to advise on how to improve things, it is rarely ever about the technology. When one asks Analysts (and based on job postings, also hiring managers) about SIEM, it’s clear the first thing that comes to mind is Splunk. ELK, Sentinel, etc. I would estimate the technology-only focus with SIEM to be the norm rather than the exception, and it comes hand-in-hand with a failure to detect privilege elevations, and lateral movements for example.

There are some advisories that we can give out that are independent of your architecture, but many questions about SIEM configuration can only be answered by you, using your knowledge of the IT landscape in your organisation. The advisories in the referenced spreadsheet cover the “noise” part of the signal-to-noise ratio. These are events that are sure to be noise to at least a 90% level of assurance, from a security perspective.

Addtional Context on the Spreadsheet

Some context around the spreadsheet: where there is a CIS Benchmark metric for a specific Audit Subcategory, the spreadsheet follows exactly the CIS recommended setting. But there are some (e.g. DS Access –> Directory Service Access) where this subcategory was not covered by CIS. In these cases, an assessment is made based on our real-experience observations of logging volumes, versus the security (not the IT diagnostic, or other value) value of Audit Subcategories. In this case of the Directory Service Access subcategory, it can be turned off from a security perspective.

There is limited information available regarding actual experiences with specific event ID volumes. In 2018, I had the opportunity to track Windows events in a Splunk architecture for a government department. During this time, I recorded the occurrences of events over a 24-hour period on a network of approximately 150 Windows servers of various versions, some of which were quite exotic. This information has been valuable in supporting decisions related to whether or not to disable auditing.

SIEM Forwarder Filtering

There is another option offered by some SIEM vendors and that is to filter events by Event ID. Overall, the more resource-friendly approach is to prevent the events being generated at source, but in many cases this may not be feasible. Splunk for example allows you to filter at forwarders (via the inputs.conf file on the Splunk forwarder. This file is usually located in the $SPLUNK_HOME/etc/system/local/ directory … more info – BTW it looks like Splunk agrees with us on the 4662 event mentioned as an example above. Yay!).

Credits and Disclaimers

Windows Events are sometimes tricky to understand, both with respect of what the developers intended with those events, and the conditions under which they are generated. Sometimes with Windows Events, we are completely in unknown territory, even if there is some Microsoft documentation that covers them. Here’s one example from Microsoft documentation to fill us with confidence – “This auditing subcategory should not have any events in it, but for some reason Success auditing will enable the generation of event 4985″.

Ultimately only you can decide what’s best for the health of your SOC/SIEM. Only you know your network and your applications. The document supplied here was only intended as a guide, and to aid decision making. It was not intended to make decisions for you.

The cybersecurity landscape often focuses on the more sensational aspects, such as high-profile hacks or fake influencers, which can overshadow the essential work done by countless professionals in the background. These unsung heroes are dedicated to ensuring the stability and security of our digital infrastructure, and their contributions should not be underestimated. Among those are tthe likes of Randy Franklin Smith (founder of Ultmate Windows Security) who has put together an “encyclopedia” of Windows Event IDs. The experiences shared there were used in-part to form a view on whether or not to reject or accept certain Windows Events.

Windows Vulnerability Management: A Cheat Sheet

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So its been a long time since my last post. In fact it is almost an entire calendar year. But if we ask our delusional/non-cynical (delete as appropriate) colleagues, we discover that we should try to look to the positive. The last post was on 10th September 2013. So do not focus on the fact that its nearly 1 year since my last post, focus on the 1 week between this post and the 1 year mark. That is quite something! Remember people: positivity is key. 51 weeks instead of 52. All is good.

And to make up for the proportional short-fall of pearls of wisdom, I am hereby making freely available a spreadsheet I developed: its a compendium of information with regard to Windows 2008 Server vulnerabilities. In vulnerability management, the tool (McAfee VM 7.5 in this case, but it could be any tool) produces long lists of vulnerability. Some of these can be false positives. Others will be bona fide. Then, where there is vulnerability, there is risk, and the level of that risk to the business needs to be deduced.

The response of the organisation to the above-mentioned list of vulnerability is usually an IT response – a collaboration between security and operations, or at least it should be. Security typically is not in a position to deduce the risk and / or the remedial actions by themselves. This is where the spreadsheet comes in. All of the information is in one document and the information that is needed to deduce factors such as impact, ease of exploit, risk, false positive, etc…its all there.

Operating system security checklists are as thin on the ground (and in their content) as they are critical in the prevention (and also detection) world. Work in this area is seen as boring and unsexy. It doesn’t involve anything that could get you a place as a speaker at a Black Hat conference. There is nothing in this realm that involves some fanciful breach technique.

Overall, forget perimeter firewalls and anti-virus – operating system security is now the front line in the battle against unauthorised access.

The CIS Benchmarks are quoted by many as a source of operating system configuration security check items and fair play to the folks at CIS for producing these documents.

The columns are as such:

  • “CIS” : the CIS subtitle for the vulnerability
  • “Recommended VM Test”: yes or no, is this a test that is worth doing? (not all of them are worth it, some are outdated, some are just silly)
  • “McAfee Test Available”: yes or no
  • “McAfee Test ID”: numeric code of the test pattern with McAfee VM 7.5
  • “Comments”: summary of the CIS text that describes the vulnerability
  • “Test / Reg Key”: the registry key to check, or other test for the vulnerability
  • “Group Policy”: The GPO value related to the vulnerability if applicable
  • “Further comments”: Some rationale from experience. For example, likelihood of being a false positive, impact, risk, ease of exploit, how to exploit. Generally – more details that can help the Analyst when interfacing with Windows support staff.
  • “McAfee VM test notes”: This is a scratchpad for the Analyst to make notes, as a reference for any other Analysts who may be performing some testing. For example, if the test regularly yields a false positive, note the fact here.
  • “References”: URLs and other material that give some background information. Mostly these are relevant Microsoft Technet articles.

MVM-CIS-Spreadoe

So if anyone would like a copy of this spread sheet, please don’t hesitate to contact me. No – I will not spam you or share your contact details.