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The following analytic detects the execution of regasm.exe establishing a network connection to a public IP address, excluding private IP ranges. This detection leverages Sysmon EventID 3 logs to identify such behavior. This activity is significant as regasm.exe is a legitimate Microsoft-signed binary that can be exploited to bypass application control mechanisms. If confirmed malicious, this behavior could indicate an adversary's attempt to establish a remote Command and Control (C2) channel, potentially leading to privilege escalation and further malicious actions within the environment.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-24
  • Author: Michael Haag, Splunk
  • ID: 07921114-6db4-4e2e-ae58-3ea8a52ae93f




ID Technique Tactic
T1218 System Binary Proxy Execution Defense Evasion
T1218.009 Regsvcs/Regasm Defense Evasion
Kill Chain Phase
  • Exploitation
  • DE.CM
  • CIS 10
`sysmon` EventID=3 dest_ip!= dest_ip!= dest_ip!= process_name=regasm.exe  
| stats count min(_time) as firstTime max(_time) as lastTime by dest, user, process_name, src_ip, dest_ip 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `detect_regasm_with_network_connection_filter`


The SPL above uses the following Macros:

:information_source: detect_regasm_with_network_connection_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • EventID
  • dest_ip
  • process_name
  • dest
  • user
  • src_ip
  • dest_host
  • dest_ip

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

Although unlikely, limited instances of regasm.exe with a network connection may cause a false positive. Filter based endpoint usage, command line arguments, or process lineage.

Associated Analytic Story


Risk Score Impact Confidence Message
80.0 80 100 An instance of $process_name$ contacting a remote destination was identified on endpoint $dest$ by user $user$. This behavior is not normal for $process_name$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.


Test Dataset

Replay any dataset to Splunk Enterprise by using our tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 4