HTML Help HH.EXE Suspicious Child Process

Severity: high
Author: Maxim Pavlunin, Nasreddine Bencherchali (Nextron Systems)
Source: upstream

Detects a suspicious child process of a Microsoft HTML Help (HH.exe)

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566` Phishing, `T1566.001` Phishing: Spearphishing Attachment
Execution	`T1047` Windows Management Instrumentation, `T1059.001` Command and Scripting Interpreter: PowerShell, `T1059.003` Command and Scripting Interpreter: Windows Command Shell, `T1059.005` Command and Scripting Interpreter: Visual Basic, `T1059.007` Command and Scripting Interpreter: JavaScript
Defense Evasion	`T1218` System Binary Proxy Execution, `T1218.001` System Binary Proxy Execution: Compiled HTML File, `T1218.010` System Binary Proxy Execution: Regsvr32, `T1218.011` System Binary Proxy Execution: Rundll32

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation
Security-Auditing	4688	A new process has been created.

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\CertReq.exe'
Image|endswith: '\CertUtil.exe'
Image|endswith: '\MSHTA.EXE'
Image|endswith: '\MSbuild.exe'
Image|endswith: '\cmd.exe'
Image|endswith: '\cscript.exe'
Image|endswith: '\installutil.exe'
Image|endswith: '\msiexec.exe'
Image|endswith: '\powershell.exe'
Image|endswith: '\pwsh.exe'
Image|endswith: '\regsvr32.exe'
Image|endswith: '\rundll32.exe'
Image|endswith: '\schtasks.exe'
Image|endswith: '\wmic.exe'
Image|endswith: '\wscript.exe'
ParentImage|endswith: '\hh.exe'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.