IMPORTANT: No additional bug fixes or documentation updates
will be released for this version. For the latest information, see the
current release documentation.
Network Connection via Certutil
editNetwork Connection via Certutil
editIdentifies certutil.exe
making a network connection. Adversaries could abuse certutil.exe
to download a certificate, or malware, from a remote URL.
Rule type: eql
Rule indices:
- winlogbeat-*
- logs-endpoint.events.*
- logs-windows.*
Severity: low
Risk score: 21
Runs every: 5m
Searches indices from: now-9m (Date Math format, see also Additional look-back time
)
Maximum alerts per execution: 100
References:
Tags:
- Elastic
- Host
- Windows
- Threat Detection
- Command and Control
Version: 7
Rule authors:
- Elastic
Rule license: Elastic License v2
Investigation guide
edit## Triage and analysis ### Investigating Network Connection via Certutil Attackers can abuse `certutil.exe` to download malware, offensive security tools, and certificates from external sources in order to take the next steps in a compromised environment. This rule looks for network events where `certutil.exe` contacts IP ranges other than the ones specified in [IANA IPv4 Special-Purpose Address Registry](https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml) #### Possible investigation steps - Investigate the script execution chain (parent process tree). - Investigate other alerts related to the user/host in the last 48 hours. - Investigate if the downloaded file was executed. - Determine the context in which `certutil.exe` and the file were run. - Retrieve the file downloaded and: - Use a sandboxed malware analysis system to perform analysis. - Observe attempts of contacting external domains and addresses. - Use the PowerShell Get-FileHash cmdlet to get the SHA-256 hash value of the file. - Search for the existence of this file in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc. ### False positive analysis - This mechanism can be used legitimately. If trusted software uses this command and the triage has not identified anything suspicious, this alert can be closed as a false positive. - If this activity is expected and noisy in your environment, consider adding exceptions — preferably with a combination of user and command line conditions. ### Response and remediation - Initiate the incident response process based on the outcome of the triage. - Isolate the involved host to prevent further post-compromise behavior. - If the triage identified malware, search the environment for additional compromised hosts. - Implement any temporary network rules, procedures, and segmentation required to contain the malware.
Rule query
editsequence by process.entity_id [process where process.name : "certutil.exe" and event.type == "start"] [network where process.name : "certutil.exe" and not cidrmatch(destination.ip, "10.0.0.0/8", "127.0.0.0/8", "169.254.0.0/16", "172.16.0.0/12", "192.0.0.0/24", "192.0.0.0/29", "192.0.0.8/32", "192.0.0.9/32", "192.0.0.10/32", "192.0.0.170/32", "192.0.0.171/32", "192.0.2.0/24", "192.31.196.0/24", "192.52.193.0/24", "192.168.0.0/16", "192.88.99.0/24", "224.0.0.0/4", "100.64.0.0/10", "192.175.48.0/24", "198.18.0.0/15", "198.51.100.0/24", "203.0.113.0/24", "240.0.0.0/4", "::1", "FE80::/10", "FF00::/8")]
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Command and Control
- ID: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
-
Technique:
- Name: Ingress Tool Transfer
- ID: T1105
- Reference URL: https://attack.mitre.org/techniques/T1105/