Password Protected ZIP File Opened (Email Attachment)

Severity: high
Author: Florian Roth (Nextron Systems)
Source: upstream

Detects the extraction of password protected ZIP archives. See the filename variable for more details on which file has been opened.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1566.001` Phishing: Spearphishing Attachment
Defense Evasion	`T1027` Obfuscated Files or Information

Event coverage

Provider	Event ID	Title
Security-Auditing	5379	Credential Manager credentials were read.

Stages and Predicates

Stage 1: `selection`

TargetName|contains: 'Microsoft_Windows_Shell_ZipFolder:filename'
TargetName|contains: '\Temporary Internet Files\Content.Outlook'

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.

Field	Kind	Values
`TargetName`	match	`Microsoft_Windows_Shell_ZipFolder:filename` corpus 3 (sigma 3) `\Temporary Internet Files\Content.Outlook` corpus 2 (sigma 2)

Neighbors

Broader alternatives (more inclusive than this rule)

These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.

Password Protected ZIP File Opened [sigma] (drops 1 filter this rule applies) (first-stage match only; downstream stages may differ)
Password Protected ZIP File Opened (Suspicious Filenames) [sigma] (drops 1 filter this rule applies) (first-stage match only; downstream stages may differ)