IMPORTANT: No additional bug fixes or documentation updates
will be released for this version. For the latest information, see the
current release documentation.
Mimikatz Memssp Log File Detected
editMimikatz Memssp Log File Detected
editIdentifies the password log file from the default Mimikatz memssp module.
Rule type: eql
Rule indices:
- winlogbeat-*
- logs-endpoint.events.*
- logs-windows.*
Severity: high
Risk score: 73
Runs every: 5m
Searches indices from: now-9m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References: None
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Credential Access
Version: 5
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
edit## Triage and analysis. ### Investigating Mimikatz Memssp Log File Detected [Mimikatz](https://github.com/gentilkiwi/mimikatz) is an open-source tool used to collect, decrypt, and/or use cached credentials. This tool is commonly abused by adversaries during the post-compromise stage where adversaries have gained an initial foothold on an endpoint and are looking to elevate privileges and seek out additional authentication objects such as tokens/hashes/credentials that can then be used to laterally move and pivot across a network. This rule looks for the creation of a file named `mimilsa.log`, which is generated when using the Mimikatz misc::memssp module, which injects a malicious Windows SSP to collect locally authenticated credentials, which includes the computer account password, running service credentials, and any accounts that logon. #### Possible investigation steps - Investigate script execution chain (parent process tree). - Investigate other alerts related to the user/host in the last 48 hours. - Scope potentially compromised accounts. Analysts can do this by searching for login events (e.g., 4624) to the target host. - Retrieve and inspect the log file contents. - By default, the log file is created in the same location as the DLL file. - Search for DLL files created in the location, and retrieve any DLLs that are not signed: - Use the PowerShell Get-FileHash cmdlet to get the SHA-256 hash value of these files. - Search for the existence of these files in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc. ### False positive analysis - This file name `mimilsa.log` should not legitimately be created. ### Related rules - Mimikatz Powershell Module Activity - ac96ceb8-4399-4191-af1d-4feeac1f1f46 ### Response and remediation - Initiate the incident response process based on the outcome of the triage. - Isolate the involved hosts to prevent further post-compromise behavior. - If the host is a Domain Controller (DC): - Activate your incident response plan for total Active Directory compromise. - Review the permissions of users that can access the DCs. - Reset passwords for all compromised accounts. - Disable remote login for compromised user accounts. - Reboot the host to remove the injected SSP from memory. - Reimage the host operating system or restore compromised files to clean versions. ## Config If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.
Rule query
editfile where file.name : "mimilsa.log" and process.name : "lsass.exe"
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
-
Technique:
- Name: OS Credential Dumping
- ID: T1003
- Reference URL: https://attack.mitre.org/techniques/T1003/