IMPORTANT: No additional bug fixes or documentation updates
will be released for this version. For the latest information, see the
current release documentation.
Archive File with Unusual Extensionedit
Identifies the creation of an archive file with an unusual extension. Attackers may attempt to evade detection by masquerading files using the file extension values used by image, audio, or document file types.
Rule type: eql
Rule indices:
- logs-endpoint.events.*
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: None
Tags:
- Domain: Endpoint
- OS: Windows
- Use Case: Threat Detection
- Tactic: Defense Evasion
- Data Source: Elastic Defend
- Rule Type: BBR
Version: 1
Rule authors:
- Elastic
Rule license: Elastic License v2
Rule queryedit
file where host.os.type == "windows" and event.action != "deletion" and
/* common archive file headers - Rar, 7z, GZIP, MSCF, XZ, ZIP */
file.Ext.header_bytes : ("52617221*", "377ABCAF271C*", "1F8B*", "4d534346*", "FD377A585A00*", "504B0304*", "504B0708*") and
(
/* common image file extensions */
file.extension : ("jpg", "jpeg", "emf", "tiff", "gif", "png", "bmp", "ico", "fpx", "eps", "inf") or
/* common audio and video file extensions */
file.extension : ("mp3", "wav", "avi", "mpeg", "flv", "wma", "wmv", "mov", "mp4", "3gp") or
/* common document file extensions */
(file.extension : ("doc", "docx", "rtf", "ppt", "pptx", "xls", "xlsx") and
/* exclude ZIP file header values for OPENXML documents */
not file.Ext.header_bytes : ("504B0304*", "504B0708*"))
) and
not (process.executable : "?:\\Windows\\System32\\inetsrv\\w3wp.exe" and file.path : "?:\\inetpub\\temp\\IIS Temporary Compressed Files\\*")
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
-
Technique:
- Name: Masquerading
- ID: T1036
- Reference URL: https://attack.mitre.org/techniques/T1036/
-
Sub-technique:
- Name: Masquerade File Type
- ID: T1036.008
- Reference URL: https://attack.mitre.org/techniques/T1036/008/