Every organization needs to collect logs from multiple sources in order to put them in either a log collector or SIEM (or a dedicated audit trail solution). And there are two options for that – using an agent and agentless.
Using an agent is easy – you install a piece of software on each machine that generates logs and it forwards them wherever needed. This is however not preferred by many organizations as it complicates things – upgrading to new versions, keeping track of dozens of configurations, and potentially impacting performance of the target machines.
So some organizations prefer to collect logs remotely, or use standard tooling, already present on the target machine. For Linux that’s typically syslog, where forwarding is configured. Logs can also be read remotely via SCP/SSH.
However, on Windows things are less straightforward. You need to access the Windows Event Log facility remotely, but there is barely a single place that describes all the required steps. This blogpost comes close, but I’d like to provide the full steps, as there are many, many things that one may miss. It is a best practice to use a non-admin, service account for that and you have to give multiple permissions to allow reading the event logs remotely.
There are also multiple ways to read the logs remotely:
- Through the Event Viewer UI – it’s the simplest to get right, as only one domain group is required for access
- Through Win32 native API calls (and DCOM) – i.e. EvtOpenSession and the related methods
- Through PowerShell Get-WinEvent (Get-EventLog is a legacy cmdlet that doesn’t support remoting)
- Through WMI directly (e.g. this or this. To be honest, I don’t know whether the native calls and the powershell commands don’t use WMI and/or CIM underneath as well – probably.
So, in order to get these options running, the following configurations have to be done:
- Allow the necessary network connections to the target machines (through network rules and firewall rules, if applicable)
- Go to Windows Firewall -> Inbound rules and enable the rules regarding “Remote log management”
- Create a service account and configure it in the remote collector. The other option is to have an account on the collector machine that is given the proper access, so that you can use the integrated AD authentication
- Add the account to the following domain groups: Event log readers, Distributed COM users. The linked article above mentions “Remote management users” as well, but that’s optional if you just want to read the logs
- Give the “Manage auditing and security log” privilege to the service account through group policies (GPO) or via “local security policy”. Find it under User Rights Assignment > Manage auditing and security log
- Give WMI access – open “wmimgmt” -> right click -> properties > Security -> Advanced and allow the service account to “Execute Methods”, “Provider Write”, “Enable Account”, “Remote Enable”. To be honest, I’m not sure exactly which folder that should be applied to, and applying it to the root may be too wide, so you’d have to experiment
- Give registry permissions: Regedit -> Local machine -> System\CurrentControlSet\Services\eventlog\Security -> right click -> permissions and add the service account. According to the linked post you also have to modify a particular registry entry, but that’s not required just for reading the log. This step is probably the most bizarre and unexpected one.
- Make sure you have DCOM rights. This comes automatically wit the DCOM group, but double check via DCOMCnfg -> right click -> COM security
- Grant permissions for the service account on c:\windows\system32\winevt. This step is not required for “simple” reading of the logs, but I’ve seen it in various places, so in some scenarios you might need to check it
- Make sure the application or service that is reading the logs remotely has sufficient permissions – it can usually run with admin privileges, because it’s on a separate, dedicated machine.
- Restart services – that is optional, but can be done just in case: Restart “Windows Remote Management (WS-Management)” and “Windows Event Log” on the target machine
As you can see, there are many things that you can miss, and there isn’t a single place in any documentation to list those steps (though there are good guides like this that go in a slightly different direction).
I can’t but make a high-level observation here – the need to do everything above is an example of how security measures can “explode” and become really hard to manage. There are many service, groups, privileges, policies, inbound rules and whatnot, instead of just “Allow remote log reading for this user”. I know it’s inherently complex, but maybe security products should make things simpler by providing recipes for typical scenarios. Following guides in some blog is definitely worse than running a predefined set of commands. And running the “Allow remote access to event log” recipe would do just what you need. Of course, knowing which recipe to run and how to parameterize it would require specific knowledge, but you can’t do security without trained experts.
The post Remote Log Collection on Windows appeared first on Bozho's tech blog.