File Compressed or Archived into Common Format by Unsigned Process

Detects files being compressed or archived into common formats by unsigned processes. This is a common technique used to obfuscate files to evade detection or to staging data for exfiltration.

Rule type: eql
Rule indices:

logs-endpoint.events.file-*

Rule Severity: low
Risk Score: 21
Runs every:
Searches indices from: now-9m
Maximum alerts per execution: ?
References:

https://en.wikipedia.org/wiki/List_of_file_signatures

Tags:

Data Source: Elastic Defend
Domain: Endpoint
OS: macOS
OS: Windows
Tactic: Collection
Rule Type: BBR

Version: ?
Rule authors:

Elastic

Rule license: Elastic License v2

Rule Query

		file where host.os.type == "windows" and event.type in ("creation", "change") and
 process.executable != null and process.code_signature.trusted != true and
 file.Ext.header_bytes : (
                          /* compression formats */
                          "1F9D*",             /* tar zip, tar.z (Lempel-Ziv-Welch algorithm) */
                          "1FA0*",             /* tar zip, tar.z (LZH algorithm) */
                          "425A68*",           /* Bzip2 */
                          "524E4301*",         /* Rob Northen Compression */
                          "524E4302*",         /* Rob Northen Compression */
                          "4C5A4950*",         /* LZIP */
                          "504B0*",            /* ZIP */
                          "526172211A07*",     /* RAR compressed */
                          "44434D0150413330*", /* Windows Update Binary Delta Compression file */
                          "50413330*",         /* Windows Update Binary Delta Compression file */
                          "377ABCAF271C*",     /* 7-Zip */
                          "1F8B*",             /* GZIP */
                          "FD377A585A00*",     /* XZ, tar.xz */
                          "7801*",	           /* zlib: No Compression (no preset dictionary) */
                          "785E*",	           /* zlib: Best speed (no preset dictionary) */
                          "789C*",	           /* zlib: Default Compression (no preset dictionary) */
                          "78DA*", 	           /* zlib: Best Compression (no preset dictionary) */
                          "7820*",	           /* zlib: No Compression (with preset dictionary) */
                          "787D*",	           /* zlib: Best speed (with preset dictionary) */
                          "78BB*",	           /* zlib: Default Compression (with preset dictionary) */
                          "78F9*",	           /* zlib: Best Compression (with preset dictionary) */
                          "62767832*",         /* LZFSE */
                          "28B52FFD*",         /* Zstandard, zst */
                          "5253564B44415441*", /* QuickZip rs compressed archive */
                          "2A2A4143452A2A*",   /* ACE */

                          /* archive formats */
                          "2D686C302D*",       /* lzh */
                          "2D686C352D*",       /* lzh */
                          "303730373037*",     /* cpio */
                          "78617221*",         /* xar */
                          "4F4152*",           /* oar */
                          "49536328*"          /* cab archive */
 )

	

Framework: MITRE ATT&CK

Tactic:
- Name: Collection
- Id: TA0009
- Reference URL: https://attack.mitre.org/tactics/TA0009/
Technique:
- Name: Data Staged
- Id: T1074
- Reference URL: https://attack.mitre.org/techniques/T1074/
Sub Technique:
- Name: Local Data Staging
- Id: T1074.001
- Reference URL: https://attack.mitre.org/techniques/T1074/001/
Technique:
- Name: Archive Collected Data
- Id: T1560
- Reference URL: https://attack.mitre.org/techniques/T1560/
Sub Technique:
- Name: Archive via Utility
- Id: T1560.001
- Reference URL: https://attack.mitre.org/techniques/T1560/001/

Framework: MITRE ATT&CK

Tactic:
- Name: Command and Control
- Id: TA0011
- Reference URL: https://attack.mitre.org/tactics/TA0011/
Technique:
- Name: Data Encoding
- Id: T1132
- Reference URL: https://attack.mitre.org/techniques/T1132/
Sub Technique:
- Name: Standard Encoding
- Id: T1132.001
- Reference URL: https://attack.mitre.org/techniques/T1132/001/

Framework: MITRE ATT&CK

Tactic:
- Name: Defense Evasion
- Id: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Obfuscated Files or Information
- Id: T1027
- Reference URL: https://attack.mitre.org/techniques/T1027/