diff --git a/rules/cross-platform/defense_evasion_whitespace_padding_command_line.toml b/rules/cross-platform/defense_evasion_whitespace_padding_command_line.toml new file mode 100644 index 00000000000..7bbc2e2210f --- /dev/null +++ b/rules/cross-platform/defense_evasion_whitespace_padding_command_line.toml @@ -0,0 +1,128 @@ +[metadata] +creation_date = "2025/06/30" +integration = ["endpoint", "system", "windows", "auditd_manager", "m365_defender", "crowdstrike"] +maturity = "production" +updated_date = "2025/06/30" + +[rule] +author = ["Elastic"] +description = """ +Identifies process execution events where the command line value contains a long sequence of whitespace characters or +multiple occurrences of contiguous whitespace. Attackers may attempt to evade signature-based detections by padding +their malicious command with unnecessary whitespace characters. These observations should be investigated for malicious +behavior. +""" +from = "now-9m" +language = "esql" +license = "Elastic License v2" +name = "Command Line Obfuscation via Whitespace Padding" +note = """## Triage and analysis + +### Investigating Command Line Obfuscation via Whitespace Padding + +This rule identifies process execution events where the command line value contains a long sequence of whitespace +characters or multiple occurrences of contiguous whitespace. Attackers may attempt to evade signature-based detections +by padding their malicious command with unnecessary whitespace characters. + +#### Possible investigation steps + +- Analyze the command line of the process in question for evidence of malicious code execution. +- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files +for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures. +- Investigate other alerts associated with the user/host during the past 48 hours. +- Investigate abnormal behaviors observed by the subject process such as network connections, registry or file +modifications, and any spawned child processes. +- Retrieve the process executable and determine if it is malicious: + - Use a private sandboxed malware analysis system to perform analysis. + - Observe and collect information about the following activities: + - Attempts to contact external domains and addresses. + - File and registry access, modification, and creation activities. + - Service creation and launch activities. + - Scheduled tasks creation. + - Use the PowerShell `Get-FileHash` cmdlet to get the files' SHA-256 hash values. + - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc. + +### False positive analysis + +- Alerts derived from this rule are not inherently malicious. Analysts can dismiss the alert if they don't find enough +evidence of further suspicious activity. + +### 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 temporary network rules, procedures, and segmentation to contain the malware. + - Stop suspicious processes. + - Immediately block the identified indicators of compromise (IoCs). + - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that + attackers could use to reinfect the system. +- Remove the malicious certificate from the root certificate store. +- Remove and block malicious artifacts identified during triage. +- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and +malware components. +- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are +identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business +systems, and web services. +- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector. +- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the +mean time to respond (MTTR). +""" +risk_score = 47 +rule_id = "5a876e0d-d39a-49b9-8ad8-19c9b622203b" +severity = "medium" +tags = [ + "Domain: Endpoint", + "OS: Windows", + "Use Case: Threat Detection", + "Tactic: Defense Evasion", + "Tactic: Execution", + "Resources: Investigation Guide" +] +timestamp_override = "event.ingested" +type = "esql" + +query = ''' +FROM logs-* metadata _id, _version, _index +| where event.category == "process" and event.type == "start" +// more than 100 spaces in process.command_line +| eval multi_spaces = LOCATE(process.command_line, space(100)) +| where multi_spaces > 0 +| keep user.name, host.id, host.name, process.command_line, process.executable, process.parent.executable +''' + + +[[rule.threat]] +framework = "MITRE ATT&CK" +[[rule.threat.technique]] +id = "T1027" +name = "Obfuscated Files or Information" +reference = "https://attack.mitre.org/techniques/T1027/" + +[[rule.threat.technique]] +id = "T1140" +name = "Deobfuscate/Decode Files or Information" +reference = "https://attack.mitre.org/techniques/T1140/" + + +[rule.threat.tactic] +id = "TA0005" +name = "Defense Evasion" +reference = "https://attack.mitre.org/tactics/TA0005/" +[[rule.threat]] +framework = "MITRE ATT&CK" +[[rule.threat.technique]] +id = "T1059" +name = "Command and Scripting Interpreter" +reference = "https://attack.mitre.org/techniques/T1059/" +[[rule.threat.technique.subtechnique]] +id = "T1059.001" +name = "PowerShell" +reference = "https://attack.mitre.org/techniques/T1059/001/" + + + +[rule.threat.tactic] +id = "TA0002" +name = "Execution" +reference = "https://attack.mitre.org/tactics/TA0002/"