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This detection identifies adversary use of file compression utilities (ZIP, gzip, 7z, RAR, tar) to obfuscate payloads, stage data for exfiltration, or deliver malicious archives. Key signals include compression tools spawned by unusual parent processes, self-extracting archive execution, concatenated ZIP files used to evade scanners, and shellcode compressed into registry keys. The detection focuses on behavioral anomalies such as compression utilities invoked from scripting engines, email clients, or Office applications, as well as archives extracted directly into temporary or startup directories.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.015 Compression
- Canonical reference
- https://attack.mitre.org/techniques/T1027/015/
YARA-L Detection Query
rule t1027_015_compression_suspicious {
meta:
author = "argus-v1"
description = "Detects compression tools spawned by Office, scripting hosts, or with SFX/encryption flags"
severity = "MEDIUM"
technique = "T1027.015"
tactic = "TA0005"
events:
$e.metadata.event_type = "PROCESS_LAUNCH"
$e.target.process.file.full_path = /(?i)(7z\.exe|7za\.exe|7zr\.exe|winrar\.exe|rar\.exe|unrar\.exe|winzip32\.exe|winzip64\.exe|pkzip\.exe|wzzip\.exe)$/
(
$e.principal.process.file.full_path = /(?i)(winword|excel|powerpnt|outlook|mshta|wscript|cscript|rundll32|regsvr32|msiexec)\.exe$/
or
$e.target.process.command_line = /(?i)(-sfx|-mhe|-mx9|-p[a-zA-Z0-9]{1,}|-ao)/
or
$e.target.process.command_line = /(?i)(\\Temp\\|\\AppData\\|\\ProgramData\\|\\Users\\Public\\)/
)
condition:
$e
}Chronicle YARA-L rule that triggers on compression utility execution where the parent process is a known Office application or scripting host, or where command-line flags indicate self-extracting archives, encryption, or staging in high-risk directories.
Data Sources
Required Tables
False Positives & Tuning
- Office-triggered automation for legitimate file packaging and distribution
- IT operations using self-extracting archives for software deployment
- Authorized red team exercises simulating payload delivery chains
Other platforms for T1027.015
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 17zip Self-Extracting Archive Creation from PowerShell
Expected signal: Sysmon Event ID 1: PowerShell spawning 7z.exe with -sfx, -p, -mhe flags. Sysmon Event ID 11: payload.exe created in C:\Users\Public\. DeviceProcessEvents in MDE.
- Test 2Concatenated ZIP Payload Creation
Expected signal: Sysmon Event ID 1: cmd.exe spawning 7z.exe twice. Sysmon Event ID 11: concatenated.zip created in C:\Temp\. Security Event 4688 if process auditing enabled.
- Test 3Linux gzip Compression of Shellcode Blob
Expected signal: Auditd syscall logs showing dd, gzip, and base64 invocations. Syslog entries for process execution. File creation event for /tmp/.hidden_payload.b64.
References (5)
- https://attack.mitre.org/techniques/T1027/015/
- https://perception-point.io/blog/analysis-of-a-phishing-campaign-using-concatenated-zip-files/
- https://www.ntt-review.jp/archive/ntttechnical.php?contents=ntr202203fa1.html
- https://thehackernews.com/2024/02/hackers-exploit-self-extracting-archive.html
- https://www.prevailion.com/darkwatchman-new-fileless-techniques/
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