Suspicious Network Connection Binary No CommandLine

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

Detects suspicious network connections made by a well-known Windows binary run with no command line parameters

Event coverage

Provider	Event ID	Title
Sysmon	3	Network connection

Stages and Predicates

Stage 1: `selection`

or:
CommandLine|endswith: '\dllhost.exe'
CommandLine|endswith: '\regsvr32.exe'
CommandLine|endswith: '\rundll32.exe'
or:
Image|endswith: '\dllhost.exe'
Image|endswith: '\regsvr32.exe'
Image|endswith: '\rundll32.exe'
Initiated: true

Stage 2: `not 1 of filter*`

or:
CommandLine: ''
CommandLine: null

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
`CommandLine`	ends_with	`\dllhost.exe` `\regsvr32.exe` `\rundll32.exe` corpus 2 (sigma 2)
`Image`	ends_with	`\dllhost.exe` corpus 8 (sigma 8) `\regsvr32.exe` corpus 57 (sigma 57) `\rundll32.exe` corpus 76 (sigma 76)
`Initiated`	eq	`true` corpus 40 (sigma 40)