Potentially Suspicious Regsvr32 HTTP/FTP Pattern

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

Detects regsvr32 execution to download/install/register new DLLs that are hosted on Web or FTP servers.

MITRE ATT&CK coverage

Tactic	Techniques
Defense Evasion	`T1218.010` System Binary Proxy Execution: Regsvr32

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `all of selection_img`

or:
Image|endswith: '\regsvr32.exe'
OriginalFileName: REGSVR32.EXE

Stage 2: `all of selection_flag`

or:
CommandLine|contains: ' -i'
CommandLine|contains: ' /i'

Stage 3: `all of selection_protocol`

or:
CommandLine|contains: ftp
CommandLine|contains: http

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	`-i` corpus 3 (sigma 3) `/i` `ftp` corpus 2 (sigma 2) `http` corpus 31 (sigma 31)
`Image`	ends_with	`\regsvr32.exe` corpus 57 (sigma 57)
`OriginalFileName`	eq	`REGSVR32.EXE` corpus 10 (sigma 10)