WebDav Client Execution Via Rundll32.EXE

Severity: medium
Author: Roberto Rodriguez (Cyb3rWard0g), OTR (Open Threat Research)
Source: upstream

Detects "svchost.exe" spawning "rundll32.exe" with command arguments like "C:\windows\system32\davclnt.dll,DavSetCookie". This could be an indicator of exfiltration or use of WebDav to launch code (hosted on a WebDav server).

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	`T1048.003` Exfiltration Over Alternative Protocol: Exfiltration Over Unencrypted Non-C2 Protocol

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_parent`

ParentImage|endswith: '\svchost.exe'

Stage 2: `all of selection_img`

or:
Image|endswith: '\rundll32.exe'
OriginalFileName: RUNDLL32.EXE

Stage 3: `all of selection_cli`

CommandLine|contains: 'C:\windows\system32\davclnt.dll,DavSetCookie'

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`	match	`C:\windows\system32\davclnt.dll,DavSetCookie` corpus 3 (sigma 3)
`Image`	ends_with	`\rundll32.exe` corpus 76 (sigma 76)
`OriginalFileName`	eq	`RUNDLL32.EXE` corpus 28 (sigma 25, splunk 3)
`ParentImage`	ends_with	`\svchost.exe` corpus 8 (sigma 8)

Neighbors

Stricter alternatives (narrower than this rule)

The rules below may be useful if you find the current rule is too noisy / lacks specificity.

Suspicious WebDav Client Execution Via Rundll32.EXE [sigma] (adds 4 filters) (first-stage match only; downstream stages may differ)